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Deb S, Krause J, Faria Junior PE, Kempf MA, Schwartz R, Watanabe K, Taniguchi T, Fabian J, Korn T. Excitonic signatures of ferroelectric order in parallel-stacked MoS 2. Nat Commun 2024; 15:7595. [PMID: 39217159 PMCID: PMC11366029 DOI: 10.1038/s41467-024-52011-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Accepted: 08/22/2024] [Indexed: 09/04/2024] Open
Abstract
Interfacial ferroelectricity, prevalent in various parallel-stacked layered materials, allows switching of out-of-plane ferroelectric order by in-plane sliding of adjacent layers. Its resilience against doping potentially enables next-generation storage and logic devices. However, studies have been limited to indirect sensing or visualization of ferroelectricity. For transition metal dichalcogenides, there is little knowledge about the influence of ferroelectric order on their intrinsic valley and excitonic properties. Here, we report direct probing of ferroelectricity in few-layer 3R-MoS2 using reflectance contrast spectroscopy. Contrary to a simple electrostatic perception, layer-hybridized excitons with out-of-plane electric dipole moment remain decoupled from ferroelectric ordering, while intralayer excitons with in-plane dipole orientation are sensitive to it. Ab initio calculations identify stacking-specific interlayer hybridization leading to this asymmetric response. Exploiting this sensitivity, we demonstrate optical readout and control of multi-state polarization with hysteretic switching in a field-effect device. Time-resolved Kerr ellipticity reveals direct correspondence between spin-valley dynamics and stacking order.
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Affiliation(s)
- Swarup Deb
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23, Rostock, 18059, Germany.
| | - Johannes Krause
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23, Rostock, 18059, Germany
| | - Paulo E Faria Junior
- Institute for Theoretical Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Michael Andreas Kempf
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23, Rostock, 18059, Germany
| | - Rico Schwartz
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23, Rostock, 18059, Germany
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, NIMS, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, NIMS, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Jaroslav Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040, Regensburg, Germany
| | - Tobias Korn
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23, Rostock, 18059, Germany.
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2
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Wu R, Zhang H, Ma H, Zhao B, Li W, Chen Y, Liu J, Liang J, Qin Q, Qi W, Chen L, Li J, Li B, Duan X. Synthesis, Modulation, and Application of Two-Dimensional TMD Heterostructures. Chem Rev 2024. [PMID: 39189449 DOI: 10.1021/acs.chemrev.4c00174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/28/2024]
Abstract
Two-dimensional (2D) transition metal dichalcogenide (TMD) heterostructures have attracted a lot of attention due to their rich material diversity and stack geometry, precise controllability of structure and properties, and potential practical applications. These heterostructures not only overcome the inherent limitations of individual materials but also enable the realization of new properties through appropriate combinations, establishing a platform to explore new physical and chemical properties at micro-nano-pico scales. In this review, we systematically summarize the latest research progress in the synthesis, modulation, and application of 2D TMD heterostructures. We first introduce the latest techniques for fabricating 2D TMD heterostructures, examining the rationale, mechanisms, advantages, and disadvantages of each strategy. Furthermore, we emphasize the importance of characteristic modulation in 2D TMD heterostructures and discuss some approaches to achieve novel functionalities. Then, we summarize the representative applications of 2D TMD heterostructures. Finally, we highlight the challenges and future perspectives in the synthesis and device fabrication of 2D TMD heterostructures and provide some feasible solutions.
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Affiliation(s)
- Ruixia Wu
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Hongmei Zhang
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Huifang Ma
- Innovation Center for Gallium Oxide Semiconductor (IC-GAO), National and Local Joint Engineering Laboratory for RF Integration and Micro-Assembly Technologies, College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
- School of Flexible Electronics (Future Technologies) Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, Nanjing 211816, China
| | - Bei Zhao
- School of Physics and Key Laboratory of Quantum Materials and Devices of Ministry of Education, Southeast University, Nanjing 211189, China
| | - Wei Li
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Yang Chen
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Jianteng Liu
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Jingyi Liang
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Qiuyin Qin
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Weixu Qi
- Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Liang Chen
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Jia Li
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Bo Li
- Changsha Semiconductor Technology and Application Innovation Research Institute, School of Physics and Electronics, College of Semiconductors (College of Integrated Circuits), Hunan University, Changsha 410082, China
| | - Xidong Duan
- Hunan Provincial Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
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3
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Liu Y, Yan Z, Bai R, Zhang X, Cheng X, Ren Y, Zhu Y, Zhou R, Ma H, Jiang C. Heterostrain-Induced Zeeman-like Splitting in h-BN-Encapsulated Bilayer WSe 2. NANO LETTERS 2024. [PMID: 39167714 DOI: 10.1021/acs.nanolett.4c02374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/23/2024]
Abstract
Heterostrain is predicted to induce exceptionally rich physics in atomically thin two-dimensional structures by modifying the symmetry and optical selection rules. In this work, we introduce heterostrain into WSe2 bilayers by combining h-BN encapsulation and high-temperature vacuum annealing. Nonvolatile heterostrain gives rise to a Zeeman-like splitting associated with the elliptically polarized optical emission of interlayer K-K excitons. Further manipulation of the interlayer exciton emission in an external magnetic field reveals that the Zeeman-like splitting cannot be eliminated even in a magnetic field of up to ±6 T. We propose a microscopic picture with respect to the layer and valley pseudospin to interpret the results. Our findings imply an intriguing way to encode binary information with the layer pseudospin enabled by the heterostrain and open a venue for manipulating the layer pseudospin with heterostrain engineering, optical pseudospin injection, and an external magnetic field.
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Affiliation(s)
- Yulun Liu
- College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China
| | - Zuowei Yan
- College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China
| | - Ruixue Bai
- College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China
| | - Xilin Zhang
- College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China
| | - Xiaoyu Cheng
- College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China
| | - Yanbo Ren
- College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China
| | - Yaojie Zhu
- School of Physical Science and Technology, Tiangong University, Tianjin 300387, China
| | - Rui Zhou
- School of Physical Science and Technology, Tiangong University, Tianjin 300387, China
| | - Hui Ma
- School of Physical Science and Technology, Tiangong University, Tianjin 300387, China
| | - Chongyun Jiang
- College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China
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4
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Ding P, Yan J, Wang J, Han X, Yang W, Chen H, Zhang D, Huang M, Zhao J, Yang S, Xue TT, Liu L, Dai Y, Hou Y, Zhang S, Xu X, Wang Y, Huang Y. Manipulation of Moiré Superlattice in Twisted Monolayer-multilayer Graphene by Moving Nanobubbles. NANO LETTERS 2024; 24:8208-8215. [PMID: 38913825 DOI: 10.1021/acs.nanolett.4c02548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
In the heterostructure of two-dimensional (2D) materials, many novel physics phenomena are strongly dependent on the Moiré superlattice. How to achieve the continuous manipulation of the Moiré superlattice in the same sample is very important to study the evolution of various physical properties. Here, in minimally twisted monolayer-multilayer graphene, we found that bubble-induced strain has a huge impact on the Moiré superlattice. By employing the AFM tip to dynamically and continuously move the nanobubble, we realized the modulation of the Moiré superlattice, like the evolution of regular triangular domains into long strip domain structures with single or double domain walls. We also achieved controllable modulation of the Moiré superlattice by moving multiple nanobubbles and establishing the coupling of nanobubbles. Our work presents a flexible method for continuous and controllable manipulation of Moiré superlattices, which will be widely used to study novel physical properties in 2D heterostructures.
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Affiliation(s)
- Pengfei Ding
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Jiahao Yan
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Jiakai Wang
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Xu Han
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Wenchen Yang
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Hui Chen
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Decheng Zhang
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Mengting Huang
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Jinghan Zhao
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Shiqi Yang
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Tong-Tong Xue
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Liwei Liu
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Yunyun Dai
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Yuan Hou
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong SAR, China
| | - Shuai Zhang
- Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - Xiaolong Xu
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
| | - Yeliang Wang
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
- BIT Chongqing Institute of Microelectronics and Microsystems, Chongqing 100190, China
| | - Yuan Huang
- School of Physics, School of Integrated Circuits and Electronics, Beijing Institute of Technology, Advanced Research Institute of Multidisciplinary Sciences, Beijing 100081, China
- BIT Chongqing Institute of Microelectronics and Microsystems, Chongqing 100190, China
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5
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Zhang L, Gu L, Ni R, Xie M, Park S, Jang H, Ma R, Taniguchi T, Watanabe K, Zhou Y. Electrical Control and Transport of Tightly Bound Interlayer Excitons in a MoSe_{2}/hBN/MoSe_{2} Heterostructure. PHYSICAL REVIEW LETTERS 2024; 132:216903. [PMID: 38856288 DOI: 10.1103/physrevlett.132.216903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 03/11/2024] [Accepted: 04/15/2024] [Indexed: 06/11/2024]
Abstract
Controlling interlayer excitons in Van der Waals heterostructures holds promise for exploring Bose-Einstein condensates and developing novel optoelectronic applications, such as excitonic integrated circuits. Despite intensive studies, several key fundamental properties of interlayer excitons, such as their binding energies and interactions with charges, remain not well understood. Here we report the formation of momentum-direct interlayer excitons in a high-quality MoSe_{2}/hBN/MoSe_{2} heterostructure under an electric field, characterized by bright photoluminescence (PL) emission with high quantum yield and a narrow linewidth of less than 4 meV. These interlayer excitons show electrically tunable emission energy spanning ∼180 meV through the Stark effect, and exhibit a sizable binding energy of ∼81 meV in the intrinsic regime, along with trion binding energies of a few millielectronvolts. Remarkably, we demonstrate the long-range transport of interlayer excitons with a characteristic diffusion length exceeding 10 μm, which can be attributed, in part, to their dipolar repulsive interactions. Spatially and polarization-resolved spectroscopic studies reveal rich exciton physics in the system, such as valley polarization, local trapping, and the possible existence of dark interlayer excitons. The formation and transport of tightly bound interlayer excitons with narrow linewidth, coupled with the ability to electrically manipulate their properties, open exciting new avenues for exploring quantum many-body physics, including excitonic condensate and superfluidity, and for developing novel optoelectronic devices, such as exciton and photon routers.
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Affiliation(s)
- Lifu Zhang
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Liuxin Gu
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Ruihao Ni
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Ming Xie
- Condensed Matter Theory Center, University of Maryland, College Park, Maryland 20742, USA
| | - Suji Park
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Houk Jang
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Rundong Ma
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Takashi Taniguchi
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - You Zhou
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
- Maryland Quantum Materials Center, College Park, Maryland 20742, USA
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6
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Zhai W, Li Z, Wang Y, Zhai L, Yao Y, Li S, Wang L, Yang H, Chi B, Liang J, Shi Z, Ge Y, Lai Z, Yun Q, Zhang A, Wu Z, He Q, Chen B, Huang Z, Zhang H. Phase Engineering of Nanomaterials: Transition Metal Dichalcogenides. Chem Rev 2024; 124:4479-4539. [PMID: 38552165 DOI: 10.1021/acs.chemrev.3c00931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Crystal phase, a critical structural characteristic beyond the morphology, size, dimension, facet, etc., determines the physicochemical properties of nanomaterials. As a group of layered nanomaterials with polymorphs, transition metal dichalcogenides (TMDs) have attracted intensive research attention due to their phase-dependent properties. Therefore, great efforts have been devoted to the phase engineering of TMDs to synthesize TMDs with controlled phases, especially unconventional/metastable phases, for various applications in electronics, optoelectronics, catalysis, biomedicine, energy storage and conversion, and ferroelectrics. Considering the significant progress in the synthesis and applications of TMDs, we believe that a comprehensive review on the phase engineering of TMDs is critical to promote their fundamental studies and practical applications. This Review aims to provide a comprehensive introduction and discussion on the crystal structures, synthetic strategies, and phase-dependent properties and applications of TMDs. Finally, our perspectives on the challenges and opportunities in phase engineering of TMDs will also be discussed.
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Affiliation(s)
- Wei Zhai
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Zijian Li
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Yongji Wang
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Li Zhai
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
- Hong Kong Branch of National Precious Metals Material Engineering Research Center (NPMM), City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Yao Yao
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Siyuan Li
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Lixin Wang
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Hua Yang
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Banlan Chi
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Jinzhe Liang
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Zhenyu Shi
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Yiyao Ge
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
- State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
| | - Zhuangchai Lai
- Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong 999077, China
| | - Qinbai Yun
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - An Zhang
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Zhiying Wu
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Qiyuan He
- Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Bo Chen
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
- State Key Laboratory of Organic Electronics and Information Displays & Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials (IAM), School of Chemistry and Life Sciences, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Zhiqi Huang
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Hua Zhang
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, China
- Hong Kong Branch of National Precious Metals Material Engineering Research Center (NPMM), City University of Hong Kong, Kowloon, Hong Kong 999077, China
- Hong Kong Institute for Clean Energy, City University of Hong Kong, Kowloon, Hong Kong 999077, China
- Shenzhen Research Institute, City University of Hong Kong, Shenzhen 518057, China
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7
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Xie B, Wu J, Mei J, Zhu S, Zhang R, Gu F, Watanabe K, Taniguchi T, Cai X. Resonant Tunneling-Enhanced Photoresponsivity in a Twisted Graphene van der Waals Heterostructure. NANO LETTERS 2024; 24:2870-2875. [PMID: 38407933 DOI: 10.1021/acs.nanolett.3c05131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Leveraging its ultrahigh carrier mobility, zero-bandgap linear dispersion, and extremely short response time, graphene exhibits remarkable potential in ultrafast broad-band photodetection. Nonetheless, the inherently low responsivity of graphene photodetectors, due to the low photogenerated carrier density, significantly impedes the development of practical devices. In this study, we present an improved photoresponse within a graphene-hexagonal boron nitride-graphene vertical tunnel junction device, where the crystallographic orientation of the two graphene electrodes is aligned. Through meticulous device structure design and the adjustment of bias and gate voltages, we observe a 2 orders of magnitude increase in tunneling photocurrent, which is attributed to the momentum-conserving resonant electron tunneling. The enhanced external photoresponsivity is evident across a wide temperature and spectral range and achieves 0.7 A/W for visible light excitation. This characteristic, coupled with the device's negative differential conductance, suggests a novel avenue for highly efficient photodetection and high-frequency, logic-based optoelectronics using van der Waals heterostructures.
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Affiliation(s)
- Binghe Xie
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Jiaxin Wu
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Junning Mei
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Shuangxing Zhu
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Ruan Zhang
- Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Key Laboratory of Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Feifan Gu
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
- Key Laboratory of Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-00044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-00044, Japan
| | - Xinghan Cai
- National Key Laboratory of Advanced Micro and Nano Manufacture Technology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
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8
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Yang D, Liang J, Wu J, Xiao Y, Dadap JI, Watanabe K, Taniguchi T, Ye Z. Non-volatile electrical polarization switching via domain wall release in 3R-MoS 2 bilayer. Nat Commun 2024; 15:1389. [PMID: 38360848 PMCID: PMC10869714 DOI: 10.1038/s41467-024-45709-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 02/02/2024] [Indexed: 02/17/2024] Open
Abstract
Understanding the nature of sliding ferroelectricity is of fundamental importance for the discovery and application of two-dimensional ferroelectric materials. In this work, we investigate the phenomenon of switchable polarization in a bilayer MoS2 with natural rhombohedral stacking, where the spontaneous polarization is coupled with excitonic effects through asymmetric interlayer coupling. Using optical spectroscopy and imaging techniques, we observe how a released domain wall switches the polarization of a large single domain. Our results highlight the importance of domain walls in the polarization switching of non-twisted rhombohedral transition metal dichalcogenides and open new opportunities for the non-volatile control of their optical response.
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Affiliation(s)
- Dongyang Yang
- Department of Physics and Astronomy, The University of British Columbia, Vancouver, BC, Canada
- Quantum Matter Institute, The University of British Columbia, Vancouver, BC, Canada
| | - Jing Liang
- Department of Physics and Astronomy, The University of British Columbia, Vancouver, BC, Canada
- Quantum Matter Institute, The University of British Columbia, Vancouver, BC, Canada
| | - Jingda Wu
- Department of Physics and Astronomy, The University of British Columbia, Vancouver, BC, Canada
- Quantum Matter Institute, The University of British Columbia, Vancouver, BC, Canada
| | - Yunhuan Xiao
- Department of Physics and Astronomy, The University of British Columbia, Vancouver, BC, Canada
- Quantum Matter Institute, The University of British Columbia, Vancouver, BC, Canada
| | - Jerry I Dadap
- Department of Physics and Astronomy, The University of British Columbia, Vancouver, BC, Canada
- Quantum Matter Institute, The University of British Columbia, Vancouver, BC, Canada
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Ziliang Ye
- Department of Physics and Astronomy, The University of British Columbia, Vancouver, BC, Canada.
- Quantum Matter Institute, The University of British Columbia, Vancouver, BC, Canada.
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9
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Soltero I, Kaliteevski MA, McHugh JG, Enaldiev V, Fal’ko VI. Competition of Moiré Network Sites to Form Electronic Quantum Dots in Reconstructed MoX 2/WX 2 Heterostructures. NANO LETTERS 2024; 24:1996-2002. [PMID: 38295286 PMCID: PMC10870774 DOI: 10.1021/acs.nanolett.3c04427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 01/26/2024] [Accepted: 01/26/2024] [Indexed: 02/02/2024]
Abstract
Twisted bilayers of two-dimensional semiconductors offer a versatile platform for engineering quantum states for charge carriers using moiré superlattice effects. Among the systems of recent interest are twistronic MoX2/WX2 heterostructures (X = Se or S), which undergo reconstruction into preferential stacking domains and highly strained domain wall networks, determining the electron/hole localization across moiré superlattices. Here, we present a catalogue of options for the formation of self-organized quantum dots and wires in lattice-reconstructed marginally twisted MoX2/WX2 bilayers with a relative lattice mismatch δ ≪ 1 for twist angles ranging from perfect alignment to θ ∼ 1°. On the basis of multiscale modeling taking into account twirling of domain wall networks, we analyze bilayers with both parallel and antiparallel orientations of their unit cells and describe crossovers between different positioning of band edges for electrons and holes across moiré superlattices when θ < δ and θ > δ.
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Affiliation(s)
- Isaac Soltero
- Department
of Physics and Astronomy, University of
Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
| | - Mikhail A. Kaliteevski
- Department
of Physics and Astronomy, University of
Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
| | - James G. McHugh
- Department
of Physics and Astronomy, University of
Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
| | - Vladimir Enaldiev
- Department
of Physics and Astronomy, University of
Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
| | - Vladimir I. Fal’ko
- Department
of Physics and Astronomy, University of
Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
- Henry
Royce Institute for Advanced Materials, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
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10
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Dai B, Su Y, Guo Y, Wu C, Xie Y. Recent Strategies for the Synthesis of Phase-Pure Ultrathin 1T/1T' Transition Metal Dichalcogenide Nanosheets. Chem Rev 2024; 124:420-454. [PMID: 38146851 DOI: 10.1021/acs.chemrev.3c00422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
The past few decades have witnessed a notable increase in transition metal dichalcogenide (TMD) related research not only because of the large family of TMD candidates but also because of the various polytypes that arise from the monolayer configuration and layer stacking order. The peculiar physicochemical properties of TMD nanosheets enable an enormous range of applications from fundamental science to industrial technologies based on the preparation of high-quality TMDs. For polymorphic TMDs, the 1T/1T' phase is particularly intriguing because of the enriched density of states, and thus facilitates fruitful chemistry. Herein, we comprehensively discuss the most recent strategies for direct synthesis of phase-pure 1T/1T' TMD nanosheets such as mechanical exfoliation, chemical vapor deposition, wet chemical synthesis, atomic layer deposition, and more. We also review frequently adopted methods for phase engineering in TMD nanosheets ranging from chemical doping and alloying, to charge injection, and irradiation with optical or charged particle beams. Prior to the synthesis methods, we discuss the configuration of TMDs as well as the characterization tools mostly used in experiments. Finally, we discuss the current challenges and opportunities as well as emphasize the promising fields for the future development.
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Affiliation(s)
- Baohu Dai
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Yueqi Su
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Yuqiao Guo
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Changzheng Wu
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Yi Xie
- Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
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11
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Quan J, Chen G, Linhart L, Liu Z, Taniguchi T, Watanabe K, Libisch F, Huang R, Li X. Quantifying Strain in Moiré Superlattice. NANO LETTERS 2023; 23:11510-11516. [PMID: 38085265 DOI: 10.1021/acs.nanolett.3c03115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2023]
Abstract
In twisted van der Waals (vdW) bilayers, intrinsic strain associated with the moiré superlattice and unintentionally introduced uniaxial strain may be present simultaneously. Both strains are able to lift the degeneracy of the E2g phonon modes in Raman spectra. Because of the different rotation symmetry of the two types of strain, the corresponding Raman intensity exhibits a distinct polarization dependence. We compare a 2.5° twisted MoS2 bilayer, in which the maximal intrinsic moiré strain is anticipated, and a natural MoS2 bilayer with an intentionally introduced uniaxial strain. By analyzing the frequency shift of the E2g doublet and their polarization dependence, we can not only determine the direction of unintentional uniaxial strain in the twisted bilayer but also quantify both strain components. This simple strain characterization method based on far-field Raman spectra will facilitate the studies of electronic properties of moiré superlattices under the influence of combined intrinsic and external strains.
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Affiliation(s)
- Jiamin Quan
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Ganbin Chen
- Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Lukas Linhart
- Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria
| | - Zhida Liu
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Florian Libisch
- Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria
| | - Rui Huang
- Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Xiaoqin Li
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
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12
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Xie Y, Gao Y, Chen F, Wang Y, Mao J, Liu Q, Chu S, Yang H, Ye Y, Gong Q, Feng J, Gao Y. Bright and Dark Quadrupolar Excitons in the WSe_{2}/MoSe_{2}/WSe_{2} Heterotrilayer. PHYSICAL REVIEW LETTERS 2023; 131:186901. [PMID: 37977607 DOI: 10.1103/physrevlett.131.186901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 09/25/2023] [Indexed: 11/19/2023]
Abstract
Transition metal dichalcogenide heterostructures have been extensively studied as a platform for investigating exciton physics. While heterobilayers such as WSe_{2}/MoSe_{2} have received significant attention, there has been comparatively less research on heterotrilayers, which may offer new excitonic species and phases, as well as unique physical properties. In this Letter, we present theoretical and experimental investigations on the emission properties of quadrupolar excitons (QXs), a newly predicted type of exciton, in a WSe_{2}/MoSe_{2}/WSe_{2} heterotrilayer device. Our findings reveal that the optical brightness or darkness of QXs is determined by horizontal mirror symmetry and valley and spin selection rules. Additionally, the emission intensity and energy of both bright and dark QXs can be adjusted by applying an out-of-plane electric field, due to changes in hole distribution and the Stark effect. These results not only provide experimental evidence for the existence of QXs in heterotrilayers but also uncover their novel properties, which have the potential to drive the development of new exciton-based applications.
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Affiliation(s)
- Yongzhi Xie
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Yuchen Gao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Fengyu Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Yunkun Wang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Jun Mao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Qinyun Liu
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Saisai Chu
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu 226010, China
| | - Hong Yang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu 226010, China
| | - Yu Ye
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu 226010, China
| | - Qihuang Gong
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu 226010, China
| | - Ji Feng
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Hefei National Laboratory, Hefei 230088, China
| | - Yunan Gao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu 226010, China
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13
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Jiao C, Pei S, Wu S, Wang Z, Xia J. Tuning and exploiting interlayer coupling in two-dimensional van der Waals heterostructures. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2023; 86:114503. [PMID: 37774692 DOI: 10.1088/1361-6633/acfe89] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 09/29/2023] [Indexed: 10/01/2023]
Abstract
Two-dimensional (2D) layered materials can stack into new material systems, with van der Waals (vdW) interaction between the adjacent constituent layers. This stacking process of 2D atomic layers creates a new degree of freedom-interlayer interface between two adjacent layers-that can be independently studied and tuned from the intralayer degree of freedom. In such heterostructures (HSs), the physical properties are largely determined by the vdW interaction between the individual layers,i.e.interlayer coupling, which can be effectively tuned by a number of means. In this review, we summarize and discuss a number of such approaches, including stacking order, electric field, intercalation, and pressure, with both their experimental demonstrations and theoretical predictions. A comprehensive overview of the modulation on structural, optical, electrical, and magnetic properties by these four approaches are also presented. We conclude this review by discussing several prospective research directions in 2D HSs field, including fundamental physics study, property tuning techniques, and future applications.
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Affiliation(s)
- Chenyin Jiao
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China
| | - Shenghai Pei
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China
| | - Song Wu
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China
| | - Zenghui Wang
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China
| | - Juan Xia
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China
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14
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Kaliteevski MA, Enaldiev V, Fal’ko VI. Twirling and Spontaneous Symmetry Breaking of Domain Wall Networks in Lattice-Reconstructed Heterostructures of Two-Dimensional Materials. NANO LETTERS 2023; 23:8875-8880. [PMID: 37781903 PMCID: PMC10571146 DOI: 10.1021/acs.nanolett.3c01896] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 09/23/2023] [Indexed: 10/03/2023]
Abstract
Lattice relaxation in twistronic bilayers with close lattice parameters and almost perfect crystallographic alignment of the layers results in the transformation of the moiré pattern into a sequence of preferential stacking domains and domain wall networks. Here, we show that reconstructed moiré superlattices of the perfectly aligned heterobilayers of same chalcogen transition metal dichalcogenides have broken-symmetry structures featuring twisted nodes ("twirls") of domain wall networks. The analysis of twist-angle dependence of strain characteristics for the broken-symmetry structures shows that the formation of twirl reduces the amount of hydrostatic strain around the nodes, potentially weakening their influence on the band edge energies of electrons and holes.
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Affiliation(s)
- Mikhail A. Kaliteevski
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
- Department
of Physics and Astronomy, University of
Manchester, Manchester M13 9PL, United
Kingdom
| | - Vladimir Enaldiev
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
- Department
of Physics and Astronomy, University of
Manchester, Manchester M13 9PL, United
Kingdom
| | - Vladimir I. Fal’ko
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
- Department
of Physics and Astronomy, University of
Manchester, Manchester M13 9PL, United
Kingdom
- Henry
Royce Institute for Advanced Materials, Manchester M13 9PL, U.K.
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15
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Zhang S, Liu Y, Sun Z, Chen X, Li B, Moore SL, Liu S, Wang Z, Rossi SE, Jing R, Fonseca J, Yang B, Shao Y, Huang CY, Handa T, Xiong L, Fu M, Pan TC, Halbertal D, Xu X, Zheng W, Schuck PJ, Pasupathy AN, Dean CR, Zhu X, Cobden DH, Xu X, Liu M, Fogler MM, Hone JC, Basov DN. Visualizing moiré ferroelectricity via plasmons and nano-photocurrent in graphene/twisted-WSe 2 structures. Nat Commun 2023; 14:6200. [PMID: 37794007 PMCID: PMC10550968 DOI: 10.1038/s41467-023-41773-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 09/15/2023] [Indexed: 10/06/2023] Open
Abstract
Ferroelectricity, a spontaneous and reversible electric polarization, is found in certain classes of van der Waals (vdW) materials. The discovery of ferroelectricity in twisted vdW layers provides new opportunities to engineer spatially dependent electric and optical properties associated with the configuration of moiré superlattice domains and the network of domain walls. Here, we employ near-field infrared nano-imaging and nano-photocurrent measurements to study ferroelectricity in minimally twisted WSe2. The ferroelectric domains are visualized through the imaging of the plasmonic response in a graphene monolayer adjacent to the moiré WSe2 bilayers. Specifically, we find that the ferroelectric polarization in moiré domains is imprinted on the plasmonic response of the graphene. Complementary nano-photocurrent measurements demonstrate that the optoelectronic properties of graphene are also modulated by the proximal ferroelectric domains. Our approach represents an alternative strategy for studying moiré ferroelectricity at native length scales and opens promising prospects for (opto)electronic devices.
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Affiliation(s)
- Shuai Zhang
- Department of Physics, Columbia University, New York, NY, 10027, USA.
| | - Yang Liu
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - Zhiyuan Sun
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, P.R. China
| | - Xinzhong Chen
- Department of Physics, Columbia University, New York, NY, 10027, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Baichang Li
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - S L Moore
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Song Liu
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - Zhiying Wang
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - S E Rossi
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Ran Jing
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Jordan Fonseca
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Birui Yang
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Yinming Shao
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Chun-Ying Huang
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Taketo Handa
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Lin Xiong
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Matthew Fu
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Tsai-Chun Pan
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Dorri Halbertal
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Xinyi Xu
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - Wenjun Zheng
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - P J Schuck
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - A N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - C R Dean
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - David H Cobden
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - M M Fogler
- Department of Physics, University of California, San Diego, La Jolla, CA, 92093, USA
| | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, 10027, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA.
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16
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Sebait R, Rosati R, Yun SJ, Dhakal KP, Brem S, Biswas C, Puretzky A, Malic E, Lee YH. Sequential order dependent dark-exciton modulation in bi-layered TMD heterostructure. Nat Commun 2023; 14:5548. [PMID: 37684279 PMCID: PMC10491585 DOI: 10.1038/s41467-023-41047-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 08/22/2023] [Indexed: 09/10/2023] Open
Abstract
We report the emergence of dark-excitons in transition-metal-dichalcogenide (TMD) heterostructures that strongly rely on the stacking sequence, i.e., momentum-dark K-Q exciton located exclusively at the top layer of the heterostructure. The feature stems from band renormalization and is distinct from those of typical neutral excitons or trions, regardless of materials, substrates, and even homogeneous bilayers, which is further confirmed by scanning tunneling spectroscopy. To understand the unusual stacking sequence, we introduce the excitonic Elliot formula by imposing strain exclusively on the top layer that could be a consequence of the stacking process. We further find that the intensity ratio of Q- to K-excitons in the same layer is inversely proportional to laser power, unlike for conventional K-K excitons. This can be a metric for engineering the intensity of dark K-Q excitons in TMD heterostructures, which could be useful for optical power switches in solar panels.
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Affiliation(s)
- Riya Sebait
- Deparment of Energy Science (DOES), Sungkyunkwan University, Suwon, 16419, Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, Marburg, 35032, Germany
| | - Seok Joon Yun
- Center for Nanophase Materials Sciences (CNMS), Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Krishna P Dhakal
- Deparment of Energy Science (DOES), Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Marburg, 35032, Germany
| | - Chandan Biswas
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Alexander Puretzky
- Center for Nanophase Materials Sciences (CNMS), Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, Marburg, 35032, Germany.
| | - Young Hee Lee
- Deparment of Energy Science (DOES), Sungkyunkwan University, Suwon, 16419, Republic of Korea.
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon, 16419, Republic of Korea.
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17
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Ko K, Yuk A, Engelke R, Carr S, Kim J, Park D, Heo H, Kim HM, Kim SG, Kim H, Taniguchi T, Watanabe K, Park H, Kaxiras E, Yang SM, Kim P, Yoo H. Operando electron microscopy investigation of polar domain dynamics in twisted van der Waals homobilayers. NATURE MATERIALS 2023; 22:992-998. [PMID: 37365226 DOI: 10.1038/s41563-023-01595-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 05/30/2023] [Indexed: 06/28/2023]
Abstract
Conventional antiferroelectric materials with atomic-scale anti-aligned dipoles undergo a transition to a ferroelectric (FE) phase under strong electric fields. The moiré superlattice formed in the twisted stacks of van der Waals crystals exhibits polar domains alternating in moiré length with anti-aligned dipoles. In this moiré domain antiferroelectic (MDAF) arrangement, the distribution of electric dipoles is distinguished from that of two-dimensional FEs, suggesting dissimilar domain dynamics. Here we performed an operando transmission electron microscopy investigation on twisted bilayer WSe2 to observe the polar domain dynamics in real time. We find that the topological protection, provided by the domain wall network, prevents the MDAF-to-FE transition. As one decreases the twist angle, however, this transition occurs as the domain wall network disappears. Exploiting stroboscopic operando transmission electron microscopy on the FE phase, we measure a maximum domain wall velocity of 300 μm s-1. Domain wall pinnings by various disorders limit the domain wall velocity and cause Barkhausen noises in the polarization hysteresis loop. Atomic-scale analysis of the pinning disorders provides structural insight on how to improve the switching speed of van der Waals FEs.
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Affiliation(s)
- Kahyun Ko
- Department of Physics, Sogang University, Seoul, Republic of Korea
| | - Ayoung Yuk
- Department of Physics, Sogang University, Seoul, Republic of Korea
| | - Rebecca Engelke
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Stephen Carr
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Physics, Brown University, Providence, RI, USA
| | - Junhyung Kim
- Department of Physics, Sogang University, Seoul, Republic of Korea
| | - Daesung Park
- Department of Physics, Sogang University, Seoul, Republic of Korea
| | - Hoseok Heo
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Hyun-Mi Kim
- Korea Electronics Technolgy Institute, Seongnam, Republic of Korea
| | - Seul-Gi Kim
- Korea Electronics Technolgy Institute, Seongnam, Republic of Korea
| | - Hyeongkeun Kim
- Korea Electronics Technolgy Institute, Seongnam, Republic of Korea
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Hongkun Park
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Efthimios Kaxiras
- Department of Physics, Harvard University, Cambridge, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Sang Mo Yang
- Department of Physics, Sogang University, Seoul, Republic of Korea.
| | - Philip Kim
- Department of Physics, Harvard University, Cambridge, MA, USA.
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
| | - Hyobin Yoo
- Department of Physics, Sogang University, Seoul, Republic of Korea.
- Institute of Emergent Materials, Sogang University, Seoul, Republic of Korea.
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18
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Anderson E, Fan FR, Cai J, Holtzmann W, Taniguchi T, Watanabe K, Xiao D, Yao W, Xu X. Programming correlated magnetic states with gate-controlled moiré geometry. Science 2023:eadg4268. [PMID: 37347950 DOI: 10.1126/science.adg4268] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 06/08/2023] [Indexed: 06/24/2023]
Abstract
The ability to control the underlying lattice geometry of a system may enable transitions between emergent quantum ground states. Here, we report in-situ gate switching between honeycomb and triangular lattice geometries of an electron many-body Hamiltonian in R-stacked MoTe2 moiré bilayers, resulting in switchable magnetic exchange interactions. At zero electric field, we observe a correlated ferromagnetic insulator near one hole per moiré unit cell with a widely tunable Curie temperature up to 14K. Applying an electric field switches the system into a half-filled triangular lattice with antiferromagnetic interactions; further doping this layer-polarized superlattice tunes the antiferromagnetic exchange interaction back to ferromagnetic. Our work demonstrates R-stacked MoTe2 moirés to be a laboratory for engineering correlated states with nontrivial topology.
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Affiliation(s)
- Eric Anderson
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Feng-Ren Fan
- Department of Physics, University of Hong Kong, Hong Kong, China
- HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, Hong Kong, China
| | - Jiaqi Cai
- Department of Physics, University of Washington, Seattle, WA, USA
| | | | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Di Xiao
- Department of Physics, University of Washington, Seattle, WA, USA
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
| | - Wang Yao
- Department of Physics, University of Hong Kong, Hong Kong, China
- HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, Hong Kong, China
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
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19
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Zhao S, Li Z, Huang X, Rupp A, Göser J, Vovk IA, Kruchinin SY, Watanabe K, Taniguchi T, Bilgin I, Baimuratov AS, Högele A. Excitons in mesoscopically reconstructed moiré heterostructures. NATURE NANOTECHNOLOGY 2023; 18:572-579. [PMID: 36973398 DOI: 10.1038/s41565-023-01356-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Accepted: 02/21/2023] [Indexed: 06/18/2023]
Abstract
Moiré effects in vertical stacks of two-dimensional crystals give rise to new quantum materials with rich transport and optical phenomena that originate from modulations of atomic registries within moiré supercells. Due to finite elasticity, however, the superlattices can transform from moiré-type to periodically reconstructed patterns. Here we expand the notion of such nanoscale lattice reconstruction to the mesoscopic scale of laterally extended samples and demonstrate rich consequences in optical studies of excitons in MoSe2-WSe2 heterostructures with parallel and antiparallel alignments. Our results provide a unified perspective on moiré excitons in near-commensurate semiconductor heterostructures with small twist angles by identifying domains with exciton properties of distinct effective dimensionality, and establish mesoscopic reconstruction as a compelling feature of real samples and devices with inherent finite size effects and disorder. Generalized to stacks of other two-dimensional materials, this notion of mesoscale domain formation with emergent topological defects and percolation networks will instructively expand the understanding of fundamental electronic, optical and magnetic properties of van der Waals heterostructures.
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Affiliation(s)
- Shen Zhao
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany.
| | - Zhijie Li
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany
| | - Xin Huang
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, P. R. China
- School of Physical Sciences, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Anna Rupp
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany
| | - Jonas Göser
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany
| | - Ilia A Vovk
- PhysNano Department, ITMO University, Saint Petersburg, Russia
| | - Stanislav Yu Kruchinin
- Center for Computational Materials Sciences, Faculty of Physics, University of Vienna, Vienna, Austria
- Nuance Communications Austria GmbH, Vienna, Austria
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Ismail Bilgin
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany
| | - Anvar S Baimuratov
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany.
| | - Alexander Högele
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany.
- Munich Center for Quantum Science and Technology (MCQST), München, Germany.
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20
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Villafañe V, Kremser M, Hübner R, Petrić MM, Wilson NP, Stier AV, Müller K, Florian M, Steinhoff A, Finley JJ. Twist-Dependent Intra- and Interlayer Excitons in Moiré MoSe_{2} Homobilayers. PHYSICAL REVIEW LETTERS 2023; 130:026901. [PMID: 36706404 DOI: 10.1103/physrevlett.130.026901] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 12/19/2022] [Indexed: 06/18/2023]
Abstract
Optoelectronic properties of van der Waals homostructures can be selectively engineered by the relative twist angle between layers. Here, we study the twist-dependent moiré coupling in MoSe_{2} homobilayers. For small angles, we find a pronounced redshift of the K-K and Γ-K excitons accompanied by a transition from K-K to Γ-K emission. Both effects can be traced back to the underlying moiré pattern in the MoSe_{2} homobilayers, as confirmed by our low-energy continuum model for different moiré excitons. We identify two distinct intralayer moiré excitons for R stacking, while H stacking yields two degenerate intralayer excitons due to inversion symmetry. In both cases, bright interlayer excitons are found at higher energies. The performed calculations are in excellent agreement with experiment and allow us to characterize the observed exciton resonances, providing insight about the layer composition and relevant stacking configuration of different moiré exciton species.
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Affiliation(s)
- Viviana Villafañe
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Malte Kremser
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Ruven Hübner
- Institut für Theoretische Physik, Universität Bremen, P.O. Box 330 440, 28334 Bremen, Germany
| | - Marko M Petrić
- Walter Schottky Institut and Department of Electrical and Computer Engineering, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Nathan P Wilson
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Andreas V Stier
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Kai Müller
- Walter Schottky Institut and Department of Electrical and Computer Engineering, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Matthias Florian
- University of Michigan, Department of Electrical Engineering and Computer Science, Ann Arbor, Michigan 48109, USA
| | - Alexander Steinhoff
- Institut für Theoretische Physik, Universität Bremen, P.O. Box 330 440, 28334 Bremen, Germany
| | - Jonathan J Finley
- Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
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21
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Tilak N, Li G, Taniguchi T, Watanabe K, Andrei EY. Moiré Potential, Lattice Relaxation, and Layer Polarization in Marginally Twisted MoS 2 Bilayers. NANO LETTERS 2023; 23:73-81. [PMID: 36576808 DOI: 10.1021/acs.nanolett.2c03676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Artificially twisted heterostructures of semiconducting transition-metal dichalcogenides (TMDs) offer unprecedented control over their electronic and optical properties via the spatial modulation of interlayer interactions and structural reconstruction. Here we study twisted MoS2 bilayers in a wide range of twist angles near 0° using scanning tunneling microscopy/spectroscopy. We investigate the twist angle dependence of the moiré pattern, which is dominated by lattice reconstruction for small angles (<2°), leading to large triangular domains with rhombohedral stacking. Local spectroscopy measurements reveal a large moiré-potential strength of 100-200 meV for angles <3°. In reconstructed regions, we see a bias-dependent asymmetry between neighboring triangular domains, which we relate to the vertical polarization that is intrinsic to rhombohedral stacked TMDs. This viewpoint is further supported by spectroscopy maps and ambient piezoresponse measurements. Our results provide a microscopic perspective of this new class of interfacial ferroelectrics and can offer clues for designing novel heterostructures that harness this effect.
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Affiliation(s)
- Nikhil Tilak
- Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Rd, Piscataway, New Jersey 08854, United States
| | - Guohong Li
- Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Rd, Piscataway, New Jersey 08854, United States
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Eva Y Andrei
- Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Rd, Piscataway, New Jersey 08854, United States
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22
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Sliding ferroelectricity in van der Waals layered γ-InSe semiconductor. Nat Commun 2023; 14:36. [PMID: 36596789 PMCID: PMC9810696 DOI: 10.1038/s41467-022-35490-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 12/06/2022] [Indexed: 01/05/2023] Open
Abstract
Two-dimensional (2D) van-der-Waals (vdW) layered ferroelectric semiconductors are highly desired for in-memory computing and ferroelectric photovoltaics or detectors. Beneficial from the weak interlayer vdW-force, controlling the structure by interlayer twist/translation or doping is an effective strategy to manipulate the fundamental properties of 2D-vdW semiconductors, which has contributed to the newly-emerging sliding ferroelectricity. Here, we report unconventional room-temperature ferroelectricity, both out-of-plane and in-plane, in vdW-layered γ-InSe semiconductor triggered by yttrium-doping (InSe:Y). We determine an effective piezoelectric constant of ∼7.5 pm/V for InSe:Y flakes with thickness of ∼50 nm, about one order of magnitude larger than earlier reports. We directly visualize the enhanced sliding switchable polarization originating from the fantastic microstructure modifications including the stacking-faults elimination and a subtle rhombohedral distortion due to the intralayer compression and continuous interlayer pre-sliding. Our investigations provide new freedom degrees of structure manipulation for intrinsic properties in 2D-vdW-layered semiconductors to expand ferroelectric candidates for next-generation nanoelectronics.
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23
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Peng J, Ren C, Zhang W, Chen H, Pan X, Bai H, Jing F, Qiu H, Liu H, Hu Z. Spatially Dependent Electronic Structures and Excitons in a Marginally Twisted Moiré Superlattice of Spiral WS 2. ACS NANO 2022; 16:21600-21608. [PMID: 36475630 DOI: 10.1021/acsnano.2c10562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Twisted two-dimensional transition metal dichalcogenide (TMD) moiré superlattices provide an additional degree of freedom to engineer electronic and optical properties. Nevertheless, controllable synthesis of marginally twisted homo TMD moiré superlattices is still a challenge. Here, physical vapor deposition grown spiral WS2 nanosheets are demonstrated to be a marginally twisted moiré superlattice using scanning tunneling microscopy and spectroscopy. Periodic moiré superlattices are found on the third layer (3L) and 4L of the spiral WS2 nanosheet owing to the marginally twisted alignment between two neighboring layers, resulting in a highly localized flat band near the valence band maximum. Their bandgap depends on atomic stacking configurations, which gives a good interpretation for split moiré excitons using photoluminescence at 77 K. This work can benefit the development of twisted homo TMD moiré superlattices and could promote the profound research of twisted TMDs in the prospective field, such as strongly correlated physics and twistronics.
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Affiliation(s)
- Jiangbo Peng
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
| | - Caixia Ren
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
| | - Weili Zhang
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
| | - Hu Chen
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
| | - Xiaoguang Pan
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
| | - Hangxin Bai
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
| | - Fangli Jing
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
| | - Hailong Qiu
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
| | - Hongjun Liu
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
| | - Zhanggui Hu
- Tianjin Key Laboratory of Functional Crystal Materials, Institute of Functional Crystals, Tianjin University of Technology, Tianjin, 300384, China
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24
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Wu J, Yang D, Liang J, Werner M, Ostroumov E, Xiao Y, Watanabe K, Taniguchi T, Dadap JI, Jones D, Ye Z. Ultrafast response of spontaneous photovoltaic effect in 3R-MoS 2-based heterostructures. SCIENCE ADVANCES 2022; 8:eade3759. [PMID: 36525495 PMCID: PMC9757740 DOI: 10.1126/sciadv.ade3759] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 11/14/2022] [Indexed: 06/17/2023]
Abstract
Rhombohedrally stacked MoS2 has been shown to exhibit spontaneous polarization down to the bilayer limit and can sustain a strong depolarization field when sandwiched between graphene. Such a field gives rise to a spontaneous photovoltaic effect without needing any p-n junction. In this work, we show that the photovoltaic effect has an external quantum efficiency of 10% for devices with only two atomic layers of MoS2 at low temperatures, and identify a picosecond-fast photocurrent response, which translates to an intrinsic device bandwidth at ∼100-GHz level. To this end, we have developed a nondegenerate pump-probe photocurrent spectroscopy technique to deconvolute the thermal and charge-transfer processes, thus successfully revealing the multicomponent nature of the photocurrent dynamics. The fast component approaches the limit of the charge-transfer speed at the graphene-MoS2 interface. The remarkable efficiency and ultrafast photoresponse in the graphene-3R-MoS2 devices support the use of ferroelectric van der Waals materials for future high-performance optoelectronic applications.
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Affiliation(s)
- Jingda Wu
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada
| | - Dongyang Yang
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada
| | - Jing Liang
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada
| | - Max Werner
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada
| | - Evgeny Ostroumov
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada
| | - Yunhuan Xiao
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Jerry I. Dadap
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada
| | - David Jones
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada
| | - Ziliang Ye
- Department of Physics and Astronomy, The University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
- Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T 1Z4, Canada
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25
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Deb S, Cao W, Raab N, Watanabe K, Taniguchi T, Goldstein M, Kronik L, Urbakh M, Hod O, Ben Shalom M. Cumulative polarization in conductive interfacial ferroelectrics. Nature 2022; 612:465-469. [PMID: 36352233 DOI: 10.1038/s41586-022-05341-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 09/13/2022] [Indexed: 11/10/2022]
Abstract
Ferroelectricity in atomically thin bilayer structures has been recently predicted1 and measured2-4 in two-dimensional materials with hexagonal non-centrosymmetric unit-cells. The crystal symmetry translates lateral shifts between parallel two-dimensional layers to sign changes in their out-of-plane electric polarization, a mechanism termed 'slide-tronics'4. These observations have been restricted to switching between only two polarization states under low charge carrier densities5-12, limiting the practical application of the revealed phenomena13. To overcome these issues, one should explore the nature of polarization in multi-layered van der Waals stacks, how it is governed by intra- and interlayer charge redistribution and to what extent it survives the addition of mobile charge carriers14. To explore these questions, we conduct surface potential measurements of parallel WSe2 and MoS2 multi-layers with aligned and anti-aligned configurations of the polar interfaces. We find evenly spaced, nearly decoupled potential steps, indicating highly confined interfacial electric fields that provide a means to design multi-state 'ladder-ferroelectrics'. Furthermore, we find that the internal polarization remains notable on electrostatic doping of mobile charge carrier densities as high as 1013 cm-2, with substantial in-plane conductivity. Using density functional theory calculations, we trace the extra charge redistribution in real and momentum spaces and identify an eventual doping-induced depolarization mechanism.
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Affiliation(s)
- Swarup Deb
- School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel
| | - Wei Cao
- Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv, Israel
| | - Noam Raab
- School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Moshe Goldstein
- School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel
| | - Leeor Kronik
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovoth, Israel
| | - Michael Urbakh
- Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv, Israel
| | - Oded Hod
- Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv, Israel
| | - Moshe Ben Shalom
- School of Physics and Astronomy, Tel Aviv University, Tel Aviv, Israel.
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26
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Sponfeldner L, Leisgang N, Shree S, Paradisanos I, Watanabe K, Taniguchi T, Robert C, Lagarde D, Balocchi A, Marie X, Gerber IC, Urbaszek B, Warburton RJ. Capacitively and Inductively Coupled Excitons in Bilayer MoS_{2}. PHYSICAL REVIEW LETTERS 2022; 129:107401. [PMID: 36112433 DOI: 10.1103/physrevlett.129.107401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 01/21/2022] [Accepted: 06/30/2022] [Indexed: 06/15/2023]
Abstract
The coupling of intralayer A and B excitons and interlayer excitons (IE) is studied in a two-dimensional semiconductor, homobilayer MoS_{2}. It is shown that the measured optical susceptibility reveals both the magnitude and the phase of the coupling constants. The IE and B excitons couple via a 0-phase (capacitive) coupling; the IE and A excitons couple via a π-phase (inductive) coupling. The IE-B and IE-A coupling mechanisms are interpreted as hole tunneling and electron-hole exchange, respectively. The couplings imply that even in a monolayer, the A and B excitons have mixed spin states. Using the IE as a sensor, the A-B intravalley exchange coupling is determined. Finally, we realize a bright and highly tunable lowest-energy momentum-direct exciton at high electric fields.
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Affiliation(s)
- Lukas Sponfeldner
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Nadine Leisgang
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Shivangi Shree
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France
| | - Ioannis Paradisanos
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Cedric Robert
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France
| | - Delphine Lagarde
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France
| | - Andrea Balocchi
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France
| | - Xavier Marie
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France
| | - Iann C Gerber
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France
| | - Bernhard Urbaszek
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, 31077 Toulouse, France
| | - Richard J Warburton
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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27
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Li K, Xiao F, Guan W, Xiao Y, Xu C, Zhang J, Lin C, Li D, Tong Q, Li SY, Pan A. Morphology Deformation and Giant Electronic Band Modulation in Long-Wavelength WS 2 Moiré Superlattices. NANO LETTERS 2022; 22:5997-6003. [PMID: 35839083 DOI: 10.1021/acs.nanolett.2c02418] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
As a lattice interference effect, moiré superlattices feature a magnification effect that they respond sensitively to both the extrinsic mechanical perturbations and intrinsic atomic reconstructions. Here, using scanning tunneling microscopy and spectroscopy, we observe that long-wavelength WS2 superlattices are reconstructed into various moiré morphologies, ranging from regular hexagons to heavily deformed ones. We show that a dedicated interplay between the extrinsic nonuniform heterostrain and the intrinsic atomic reconstruction is responsible for this interesting moiré structure evolution. Importantly, the interplay between these two factors also introduces a local inhomogeneous intralayer strain within a moiré. Contrary to the commonly reported electronic modulation that occurred at the valence band edge due to interlayer hybridization, we find that this local intralayer strain induces a strong modulation at K point of the conduction band, reaching up to 300 meV in the heavily deformed moiré. Our microscopic explorations provide valuable information in understanding the intriguing physics in TMD moirés.
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Affiliation(s)
- Kaihui Li
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Feiping Xiao
- School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Wen Guan
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Yulong Xiao
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Chang Xu
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Jinding Zhang
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Chenfang Lin
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Dong Li
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Qingjun Tong
- School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Si-Yu Li
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Anlian Pan
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
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28
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Dandu M, Gupta G, Dasika P, Watanabe K, Taniguchi T, Majumdar K. Electrically Tunable Localized versus Delocalized Intralayer Moiré Excitons and Trions in a Twisted MoS 2 Bilayer. ACS NANO 2022; 16:8983-8992. [PMID: 35679485 DOI: 10.1021/acsnano.2c00145] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Moiré superlattice (mSL)-induced sub-bands in twisted van der Waals homo- and heterostructures govern their optical and electrical properties, rendering additional degrees of freedom such as twist angle. Here, we demonstrate the moiré superlattice effects on the intralayer excitons and trions in a twisted bilayer of MoS2 of H-type stacking at marginal twist angles. We identify the emissions from localized and delocalized sub-bands of intralayer moiré excitons and show their electrical modulation by the corresponding trion formation. The electrical control of the oscillator strength of the moiré excitons also results in the strong tunability of resonant Raman scattering. We find that the gate-induced doping significantly modulates the electronic moiré potential; however, leaves the excitonic moiré confinement unaltered. This effect, coupled with variable moiré trap filling by tuning the optical excitation density, allows us to delineate the different phases of localized and delocalized moiré trions. We demonstrate that the moiré excitons exhibit strong valley coherence that changes in a striking nonmonotonic W-shape with gating due to motional narrowing. These observations from the simultaneous electrostatic control of quasiparticle-dependent moiré potential will lead to exciting effects of tunable many-body phenomena in moiré superlattices.
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Affiliation(s)
- Medha Dandu
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Garima Gupta
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Pushkar Dasika
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Kausik Majumdar
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
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29
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Wang X, Zhao Y, Kong X, Zhang Q, Ng HK, Lim SX, Zheng Y, Wu X, Watanabe K, Xu QH, Taniguchi T, Eda G, Goh KEJ, Jin S, Loh KP, Ding F, Sun W, Sow CH. Dynamic Tuning of Moiré Superlattice Morphology by Laser Modification. ACS NANO 2022; 16:8172-8180. [PMID: 35575066 DOI: 10.1021/acsnano.2c01625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In artificial van der Waals (vdW) layered devices, twisting the stacking angle has emerged as an effective strategy to regulate the electronic phases and optical properties of these systems. Along with the twist registry, the lattice reconstruction arising from vdW interlayer interaction has also inspired significant research interests. The control of twist angles is significantly important because the moiré periodicity determines the electron propagation length on the lattice and the interlayer electron-electron interactions. However, the moiré periodicity is hard to be modified after the device has been fabricated. In this work, we have demonstrated that the moiré periodicity can be precisely modulated with a localized laser annealing technique. This is achieved with regulating the interlayer lattice mismatch by the mismatched lattice constant, which originates from the variable density of sulfur vacancy generated during laser modification. The existence of sulfur vacancy is further verified by excitonic emission energy and lifetime in photoluminescence measurements. Furthermore, we also discover that the mismatched lattice constant has the equivalent contribution as the twist angle for determining the lattice mismatch. Theoretical modeling elaborates the moiré-wavelength-dependent energy variations at the interface and mimics the evolution of moiré morphology.
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Affiliation(s)
- Xinyun Wang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546
| | - Yuzhou Zhao
- Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
| | - Xiao Kong
- Centre for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan, Korea 44919
| | - Qi Zhang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
| | - Hong Kuan Ng
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
| | - Sharon Xiaodai Lim
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
| | - Yue Zheng
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546
| | - Xiao Wu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Namiki Tsukuba, Ibaraki Japan 305-0044
| | - Qing-Hua Xu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Namiki Tsukuba, Ibaraki Japan 305-0044
| | - Goki Eda
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
| | - Kuan Eng Johnson Goh
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Singapore 138634
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Song Jin
- Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
| | - Kian Ping Loh
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
| | - Feng Ding
- Centre for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan, Korea 44919
| | - Wanxin Sun
- Bruker Nano Surface Division, 30 Biopolis Street 09-01, The Matrix, Singapore 138671
| | - Chorng Haur Sow
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546
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30
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Weston A, Castanon EG, Enaldiev V, Ferreira F, Bhattacharjee S, Xu S, Corte-León H, Wu Z, Clark N, Summerfield A, Hashimoto T, Gao Y, Wang W, Hamer M, Read H, Fumagalli L, Kretinin AV, Haigh SJ, Kazakova O, Geim AK, Fal'ko VI, Gorbachev R. Interfacial ferroelectricity in marginally twisted 2D semiconductors. NATURE NANOTECHNOLOGY 2022; 17:390-395. [PMID: 35210566 PMCID: PMC9018412 DOI: 10.1038/s41565-022-01072-w] [Citation(s) in RCA: 79] [Impact Index Per Article: 39.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 01/04/2022] [Indexed: 05/19/2023]
Abstract
Twisted heterostructures of two-dimensional crystals offer almost unlimited scope for the design of new metamaterials. Here we demonstrate a room temperature ferroelectric semiconductor that is assembled using mono- or few-layer MoS2. These van der Waals heterostructures feature broken inversion symmetry, which, together with the asymmetry of atomic arrangement at the interface of two 2D crystals, enables ferroelectric domains with alternating out-of-plane polarization arranged into a twist-controlled network. The last can be moved by applying out-of-plane electrical fields, as visualized in situ using channelling contrast electron microscopy. The observed interfacial charge transfer, movement of domain walls and their bending rigidity agree well with theoretical calculations. Furthermore, we demonstrate proof-of-principle field-effect transistors, where the channel resistance exhibits a pronounced hysteresis governed by pinning of ferroelectric domain walls. Our results show a potential avenue towards room temperature electronic and optoelectronic semiconductor devices with built-in ferroelectric memory functions.
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Affiliation(s)
- Astrid Weston
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | | | - Vladimir Enaldiev
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
- Kotel'nikov Institute of Radio-engineering and Electronics, Russian Academy of Sciences, Moscow, Russia
| | - Fábio Ferreira
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Shubhadeep Bhattacharjee
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Shuigang Xu
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | | | - Zefei Wu
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Nicholas Clark
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Materials, University of Manchester, Manchester, UK
| | - Alex Summerfield
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Teruo Hashimoto
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Materials, University of Manchester, Manchester, UK
| | - Yunze Gao
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Wendong Wang
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Matthew Hamer
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Harriet Read
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Laura Fumagalli
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Andrey V Kretinin
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Materials, University of Manchester, Manchester, UK
| | - Sarah J Haigh
- National Graphene Institute, University of Manchester, Manchester, UK
- Department of Materials, University of Manchester, Manchester, UK
| | | | - A K Geim
- Department of Physics and Astronomy, University of Manchester, Manchester, UK
- National Graphene Institute, University of Manchester, Manchester, UK
| | - Vladimir I Fal'ko
- Department of Physics and Astronomy, University of Manchester, Manchester, UK.
- National Graphene Institute, University of Manchester, Manchester, UK.
- Henry Royce Institute for Advanced Materials, University of Manchester, Manchester, UK.
| | - Roman Gorbachev
- Department of Physics and Astronomy, University of Manchester, Manchester, UK.
- National Graphene Institute, University of Manchester, Manchester, UK.
- Henry Royce Institute for Advanced Materials, University of Manchester, Manchester, UK.
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31
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Wang X, Yasuda K, Zhang Y, Liu S, Watanabe K, Taniguchi T, Hone J, Fu L, Jarillo-Herrero P. Interfacial ferroelectricity in rhombohedral-stacked bilayer transition metal dichalcogenides. NATURE NANOTECHNOLOGY 2022; 17:367-371. [PMID: 35039684 DOI: 10.1038/s41565-021-01059-z] [Citation(s) in RCA: 105] [Impact Index Per Article: 52.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 11/22/2021] [Indexed: 05/27/2023]
Abstract
van der Waals materials have greatly expanded our design space of heterostructures by allowing individual layers to be stacked at non-equilibrium configurations, for example via control of the twist angle. Such heterostructures not only combine characteristics of the individual building blocks, but can also exhibit physical properties absent in the parent compounds through interlayer interactions1. Here we report on a new family of nanometre-thick, two-dimensional (2D) ferroelectric semiconductors, where the individual constituents are well-studied non-ferroelectric monolayer transition metal dichalcogenides (TMDs), namely WSe2, MoSe2, WS2 and MoS2. By stacking two identical monolayer TMDs in parallel, we obtain electrically switchable rhombohedral-stacking configurations, with out-of-plane polarization that is flipped by in-plane sliding motion. Fabricating nearly parallel-stacked bilayers enables the visualization of moiré ferroelectric domains as well as electric field-induced domain wall motion with piezoelectric force microscopy. Furthermore, by using a nearby graphene electronic sensor in a ferroelectric field transistor geometry, we quantify the ferroelectric built-in interlayer potential, in good agreement with first-principles calculations. The new semiconducting ferroelectric properties of these four new TMDs opens up the possibility of studying the interplay between ferroelectricity and their rich electric and optical properties2-5.
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Affiliation(s)
- Xirui Wang
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Kenji Yasuda
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA.
| | - Yang Zhang
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Song Liu
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | | | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
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32
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Altaiary MM, Liu E, Liang CT, Hsiao FC, van Baren J, Taniguchi T, Watanabe K, Gabor NM, Chang YC, Lui CH. Electrically Switchable Intervalley Excitons with Strong Two-Phonon Scattering in Bilayer WSe 2. NANO LETTERS 2022; 22:1829-1835. [PMID: 35201774 DOI: 10.1021/acs.nanolett.1c01590] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We report the observation of QΓ intervalley exciton in bilayer WSe2 devices encapsulated by boron nitride. The QΓ exciton resides at ∼18 meV below the QK exciton. The QΓ and QK excitons exhibit different Stark shifts under an out-of-plane electric field due to their different interlayer dipole moments. By controlling the electric field, we can switch their energy ordering and control which exciton dominates the luminescence of bilayer WSe2. Remarkably, both QΓ and QK excitons exhibit unusually strong two-phonon replicas, which are comparable to or even stronger than the one-phonon replicas. By detailed theoretical simulation, we reveal the existence of numerous (≥14) two-phonon scattering paths involving (nearly) resonant exciton-phonon scattering in bilayer WSe2. To our knowledge, such electric-field-switchable intervalley excitons with strong two-phonon replicas have not been found in any other two-dimensional semiconductors. These make bilayer WSe2 a distinctive valleytronic material with potential novel applications.
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Affiliation(s)
- Mashael M Altaiary
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
- Department of Physics, University of Jeddah, Jeddah 23445, Saudi Arabia
| | - Erfu Liu
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
| | - Ching-Tarng Liang
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Fu-Chen Hsiao
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
- Advanced Semiconductor Device and Integration Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Jeremiah van Baren
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Nathaniel M Gabor
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
- Canadian Institute for Advanced Research, 661 University Avenue, MaRS Centre West Tower, Toronto, Ontario M5G 1M1, Canada
| | - Yia-Chung Chang
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Chun Hung Lui
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
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33
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Huang D, Choi J, Shih CK, Li X. Excitons in semiconductor moiré superlattices. NATURE NANOTECHNOLOGY 2022; 17:227-238. [PMID: 35288673 DOI: 10.1038/s41565-021-01068-y] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
Semiconductor moiré superlattices represent a rapidly developing area of engineered photonic materials and a new platform to explore correlated electron states and quantum simulation. In this Review, we briefly introduce early experiments that identified new exciton resonances in transition metal dichalcogenide heterobilayers and discuss several topics including two types of transition metal dichalcogenide moiré superlattice, new optical selection rules, early evidence of moiré excitons, and how the resonant energy, dynamics and diffusion properties of moiré excitons can be controlled via the twist angle. To interpret optical spectra, it is important to measure the energy modulation within a moiré supercell. In this context, we describe a few scanning tunnelling microscopy experiments that measure the moiré potential landscape directly. Finally, we review a few recent experiments that applied excitonic optical spectroscopy to probe correlated electron phenomena in transition metal dichalcogenide moiré superlattices.
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Affiliation(s)
- Di Huang
- Physics Department and Center for Complex Quantum Systems, The University of Texas-Austin, Austin, TX, USA.
| | - Junho Choi
- Physics Department and Center for Complex Quantum Systems, The University of Texas-Austin, Austin, TX, USA
- Texas Materials Institute and Center for Dynamics and Control of Materials, The University of Texas-Austin, Austin, TX, USA
| | - Chih-Kang Shih
- Physics Department and Center for Complex Quantum Systems, The University of Texas-Austin, Austin, TX, USA
- Texas Materials Institute and Center for Dynamics and Control of Materials, The University of Texas-Austin, Austin, TX, USA
| | - Xiaoqin Li
- Physics Department and Center for Complex Quantum Systems, The University of Texas-Austin, Austin, TX, USA.
- Texas Materials Institute and Center for Dynamics and Control of Materials, The University of Texas-Austin, Austin, TX, USA.
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34
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Enaldiev VV, Ferreira F, Fal’ko VI. A Scalable Network Model for Electrically Tunable Ferroelectric Domain Structure in Twistronic Bilayers of Two-Dimensional Semiconductors. NANO LETTERS 2022; 22:1534-1540. [PMID: 35129361 PMCID: PMC9171827 DOI: 10.1021/acs.nanolett.1c04210] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 02/01/2022] [Indexed: 05/13/2023]
Abstract
Moiré structures in small-angle-twisted bilayers of two-dimensional (2D) semiconductors with a broken-symmetry interface form arrays of ferroelectric (FE) domains with periodically alternating out-of-plane polarization. Here, we propose a network theory for the tunability of such FE domain structure by applying an electric field perpendicular to the 2D crystal. Using multiscale analysis, we derive a fully parametrized string-theory-like description of the domain wall network (DWN) and show that it undergoes a qualitative change, after the arcs of partial dislocation (PD) like domain walls merge (near the network nodes) into streaks of perfect screw dislocations (PSD), which happens at a threshold displacement field dependent on the DWN period.
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Affiliation(s)
- Vladimir V. Enaldiev
- University
of Manchester, School of Physics
and Astronomy, Oxford
Road, Manchester M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
- Kotelnikov
Institute of Radio-engineering and Electronics of the RAS, Mokhovaya 11-7, Moscow 125009, Russia
| | - Fabio Ferreira
- University
of Manchester, School of Physics
and Astronomy, Oxford
Road, Manchester M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
| | - Vladimir I. Fal’ko
- University
of Manchester, School of Physics
and Astronomy, Oxford
Road, Manchester M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
- Henry
Royce Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
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35
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Zhang C, Larionov KV, Firestein KL, Fernando JFS, Lewis CE, Sorokin PB, Golberg DV. Optomechanical Properties of MoSe 2 Nanosheets as Revealed by In Situ Transmission Electron Microscopy. NANO LETTERS 2022; 22:673-679. [PMID: 35007088 DOI: 10.1021/acs.nanolett.1c03796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Free-standing few-layered MoSe2 nanosheet stacks optoelectronic signatures are analyzed by using light compatible in situ transmission electron microscopy (TEM) utilizing an optical TEM holder allowing for the simultaneous mechanical deformation, electrical probing and light illumination of a sample. Two types of deformation, namely, (i) bending of nanosheets perpendicular to their basal atomic planes and (ii) edge deformation parallel to the basal atomic planes, lead to two distinctly different optomechanical performances of the nanosheet stacks. The former deformation induces a stable but rather marginal increase in photocurrent, whereas the latter mode is prone to unstable nonsystematic photocurrent value changes and a red-shifted photocurrent spectrum. The experimental results are verified by ab initio calculations using density functional theory (DFT).
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Affiliation(s)
- Chao Zhang
- Centre for Material Science and School of Chemistry and Physics, Queensland University of Technology (QUT), 2 George Street, Brisbane, Queensland 4000, Australia
| | - Konstantin V Larionov
- National University of Science and Technology MISIS, 4 Leninsky Prospect, Moscow 119049, Russian Federation
- Moscow Institute of Physics and Technology, 9 Institutskiy Pereulok, Dolgoprudny, Moscow Region 141701, Russian Federation
| | - Konstantin L Firestein
- Centre for Material Science and School of Chemistry and Physics, Queensland University of Technology (QUT), 2 George Street, Brisbane, Queensland 4000, Australia
| | - Joseph F S Fernando
- Centre for Material Science and School of Chemistry and Physics, Queensland University of Technology (QUT), 2 George Street, Brisbane, Queensland 4000, Australia
| | - Courtney-Elyce Lewis
- Centre for Material Science and School of Chemistry and Physics, Queensland University of Technology (QUT), 2 George Street, Brisbane, Queensland 4000, Australia
| | - Pavel B Sorokin
- National University of Science and Technology MISIS, 4 Leninsky Prospect, Moscow 119049, Russian Federation
- Moscow Institute of Physics and Technology, 9 Institutskiy Pereulok, Dolgoprudny, Moscow Region 141701, Russian Federation
| | - Dmitri V Golberg
- Centre for Material Science and School of Chemistry and Physics, Queensland University of Technology (QUT), 2 George Street, Brisbane, Queensland 4000, Australia
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36
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An J, Kang J. Emergence and Tuning of Multiple Flat Bands in Twisted Bilayer γ-Graphyne. J Phys Chem Lett 2021; 12:12283-12291. [PMID: 34931832 DOI: 10.1021/acs.jpclett.1c03384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Using twisted bilayer γ-graphyne (TBGY) as an example, we show that it is possible to create multiple flat bands in carbon allotropes without the requirement of a specified magic angle. The origin of the flat bands can be understood by a simple two-level coupling model. The narrow bandwidth and strong localization of the flat band states might lead to strong correlation effects, which make TBGY a good platform for studying correlation physics. On the basis of the two-level coupling model, we further propose that the width and extent of localization of flat bands can be tuned by an energy mismatch ΔE between the two layers of TBGY, which can be realized by either applying a perpendicular electric field or introducing a heterostrain. This allows continuous modulation of TBGY from the strong-correlation regime to the medium- or weak-correlation regime, which could be utilized to study the quantum phase transition.
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Affiliation(s)
- Jiao An
- Beijing Computational Science Research Center, Beijing 100193, China
| | - Jun Kang
- Beijing Computational Science Research Center, Beijing 100193, China
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37
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Ma Q, Grushin AG, Burch KS. Topology and geometry under the nonlinear electromagnetic spotlight. NATURE MATERIALS 2021; 20:1601-1614. [PMID: 34127824 DOI: 10.1038/s41563-021-00992-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 03/19/2021] [Indexed: 06/12/2023]
Abstract
For many materials, a precise knowledge of their dispersion spectra is insufficient to predict their ordered phases and physical responses. Instead, these materials are classified by the geometrical and topological properties of their wavefunctions. A key challenge is to identify and implement experiments that probe or control these quantum properties. In this Review, we describe recent progress in this direction, focusing on nonlinear electromagnetic responses that arise directly from quantum geometry and topology. We give an overview of the field by discussing theoretical ideas, experiments and the materials that drive them. We conclude by discussing how these techniques can be combined with device architectures to uncover, probe and ultimately control quantum phases with emergent topological and correlated properties.
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Affiliation(s)
- Qiong Ma
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Physics, Boston College, Chestnut Hill, MA, USA
| | - Adolfo G Grushin
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | - Kenneth S Burch
- Department of Physics, Boston College, Chestnut Hill, MA, USA.
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38
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Song T, Sun QC, Anderson E, Wang C, Qian J, Taniguchi T, Watanabe K, McGuire MA, Stöhr R, Xiao D, Cao T, Wrachtrup J, Xu X. Direct visualization of magnetic domains and moiré magnetism in twisted 2D magnets. Science 2021; 374:1140-1144. [PMID: 34822270 DOI: 10.1126/science.abj7478] [Citation(s) in RCA: 78] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Tiancheng Song
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Qi-Chao Sun
- 3. Physikalisches Institut, University of Stuttgart, 70569 Stuttgart, Germany
| | - Eric Anderson
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Chong Wang
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Jimin Qian
- Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Michael A McGuire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Rainer Stöhr
- 3. Physikalisches Institut, University of Stuttgart, 70569 Stuttgart, Germany.,Center for Applied Quantum Technology, University of Stuttgart, 70569 Stuttgart, Germany
| | - Di Xiao
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Ting Cao
- Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA
| | - Jörg Wrachtrup
- 3. Physikalisches Institut, University of Stuttgart, 70569 Stuttgart, Germany.,Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA 98195, USA.,Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA
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39
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Wang X, Zhu J, Seyler KL, Rivera P, Zheng H, Wang Y, He M, Taniguchi T, Watanabe K, Yan J, Mandrus DG, Gamelin DR, Yao W, Xu X. Moiré trions in MoSe 2/WSe 2 heterobilayers. NATURE NANOTECHNOLOGY 2021; 16:1208-1213. [PMID: 34531556 DOI: 10.1038/s41565-021-00969-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 07/26/2021] [Indexed: 05/25/2023]
Abstract
Transition metal dichalcogenide moiré bilayers with spatially periodic potentials have emerged as a highly tunable platform for studying both electronic1-6 and excitonic4,7-13 phenomena. The power of these systems lies in the combination of strong Coulomb interactions with the capability of controlling the charge number in a moiré potential trap. Electronically, exotic charge orders at both integer and fractional fillings have been discovered2,5. However, the impact of charging effects on excitons trapped in moiré potentials is poorly understood. Here, we report the observation of moiré trions and their doping-dependent photoluminescence polarization in H-stacked MoSe2/WSe2 heterobilayers. We find that as moiré traps are filled with either electrons or holes, new sets of interlayer exciton photoluminescence peaks with narrow linewidths emerge about 7 meV below the energy of the neutral moiré excitons. Circularly polarized photoluminescence reveals switching from co-circular to cross-circular polarizations as moiré excitons go from being negatively charged and neutral to positively charged. This switching results from the competition between valley-flip and spin-flip energy relaxation pathways of photo-excited electrons during interlayer trion formation. Our results offer a starting point for engineering both bosonic and fermionic many-body effects based on moiré excitons14.
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Affiliation(s)
- Xi Wang
- Department of Physics, University of Washington, Seattle, WA, USA
- Department of Chemistry, University of Washington, Seattle, WA, USA
| | - Jiayi Zhu
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Kyle L Seyler
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Pasqual Rivera
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Huiyuan Zheng
- Department of Physics, University of Hong Kong, Hong Kong, China
- HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, Hong Kong, China
| | - Yingqi Wang
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Minhao He
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Jiaqiang Yan
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, USA
| | - David G Mandrus
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, USA
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA
| | - Daniel R Gamelin
- Department of Chemistry, University of Washington, Seattle, WA, USA
| | - Wang Yao
- Department of Physics, University of Hong Kong, Hong Kong, China.
- HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, Hong Kong, China.
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA.
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
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40
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Baek H, Brotons-Gisbert M, Campbell A, Vitale V, Lischner J, Watanabe K, Taniguchi T, Gerardot BD. Optical read-out of Coulomb staircases in a moiré superlattice via trapped interlayer trions. NATURE NANOTECHNOLOGY 2021; 16:1237-1243. [PMID: 34556832 PMCID: PMC8592839 DOI: 10.1038/s41565-021-00970-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 07/26/2021] [Indexed: 05/21/2023]
Abstract
Moiré patterns with a superlattice potential can be formed by vertically stacking two layered materials with a relative twist or lattice constant mismatch. In transition metal dichalcogenide-based systems, the moiré potential landscape can trap interlayer excitons (IXs) at specific atomic registries. Here, we report that spatially isolated trapped IXs in a molybdenum diselenide/tungsten diselenide heterobilayer device provide a sensitive optical probe of carrier filling in their immediate environment. By mapping the spatial positions of individual trapped IXs, we are able to spectrally track the emitters as the moiré lattice is filled with excess carriers. Upon initial doping of the heterobilayer, neutral trapped IXs form charged IXs (IX trions) uniformly with a binding energy of ~7 meV. Upon further doping, the empty superlattice sites sequentially fill, creating a Coulomb staircase: stepwise changes in the IX trion emission energy due to Coulomb interactions with carriers at nearest-neighbour moiré sites. This non-invasive, highly local technique can complement transport and non-local optical sensing techniques to characterize Coulomb interaction energies, visualize charge correlated states, or probe local disorder in a moiré superlattice.
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Affiliation(s)
- Hyeonjun Baek
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK.
| | - Mauro Brotons-Gisbert
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Aidan Campbell
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Valerio Vitale
- Departments of Materials and Physics and the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, London, UK
| | - Johannes Lischner
- Departments of Materials and Physics and the Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, London, UK
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Brian D Gerardot
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK.
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41
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Wilson NP, Yao W, Shan J, Xu X. Excitons and emergent quantum phenomena in stacked 2D semiconductors. Nature 2021; 599:383-392. [PMID: 34789905 DOI: 10.1038/s41586-021-03979-1] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 09/01/2021] [Indexed: 11/09/2022]
Abstract
The design and control of material interfaces is a foundational approach to realize technologically useful effects and engineer material properties. This is especially true for two-dimensional (2D) materials, where van der Waals stacking allows disparate materials to be freely stacked together to form highly customizable interfaces. This has underpinned a recent wave of discoveries based on excitons in stacked double layers of transition metal dichalcogenides (TMDs), the archetypal family of 2D semiconductors. In such double-layer structures, the elegant interplay of charge, spin and moiré superlattice structure with many-body effects gives rise to diverse excitonic phenomena and correlated physics. Here we review some of the recent discoveries that highlight the versatility of TMD double layers to explore quantum optics and many-body effects. We identify outstanding challenges in the field and present a roadmap for unlocking the full potential of excitonic physics in TMD double layers and beyond, such as incorporating newly discovered ferroelectric and magnetic materials to engineer symmetries and add a new level of control to these remarkable engineered materials.
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Affiliation(s)
- Nathan P Wilson
- Department of Physics, University of Washington, Seattle, WA, USA.,Walter Schottky Institute, Technical University of Munich, Garching, Germany.,Munich Centre for Quantum Science and Technology, Munich, Germany
| | - Wang Yao
- Department of Physics, University of Hong Kong, Hong Kong, China.,HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, Hong Kong, China
| | - Jie Shan
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA. .,Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
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42
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Zhao W, Regan EC, Wang D, Jin C, Hsieh S, Wang Z, Wang J, Wang Z, Yumigeta K, Blei M, Watanabe K, Taniguchi T, Tongay S, Yao NY, Wang F. Dynamic Tuning of Moiré Excitons in a WSe 2/WS 2 Heterostructure via Mechanical Deformation. NANO LETTERS 2021; 21:8910-8916. [PMID: 34661418 DOI: 10.1021/acs.nanolett.1c03611] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Moiré superlattices in van der Waals (vdW) heterostructures form by stacking atomically thin layers on top of one another with a twist angle or lattice mismatch. The resulting moiré potential leads to a strong modification of the band structure, which can give rise to exotic quantum phenomena ranging from correlated insulators and superconductors to moiré excitons and Wigner crystals. Here, we demonstrate the dynamic tuning of moiré potential in a WSe2/WS2 heterostructure at cryogenic temperature. We utilize the optical fiber tip of a cryogenic scanning near-field optical microscope (SNOM) to locally deform the heterostructure and measure its near-field optical response simultaneously. The deformation of the heterostructure increases the moiré potential, which leads to a red shift of the moiré exciton resonances. We observe the interlayer exciton resonance shifts up to 20 meV, while the intralayer exciton resonances shift up to 17 meV.
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Affiliation(s)
- Wenyu Zhao
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Emma C Regan
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Graduate Group in Applied Science and Technology, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley 94720, California United States
| | - Danqing Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Graduate Group in Applied Science and Technology, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley 94720, California United States
| | - Chenhao Jin
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, United States
| | - Satcher Hsieh
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley 94720, California United States
| | - Zhiyuan Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Jialu Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Zilin Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Kentaro Yumigeta
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Mark Blei
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Sefaattin Tongay
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Norman Y Yao
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley 94720, California United States
| | - Feng Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley 94720, California United States
- Kavli Energy NanoSciences Institute at University of California Berkeley and Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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43
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Helmrich S, Sampson K, Huang D, Selig M, Hao K, Tran K, Achstein A, Young C, Knorr A, Malic E, Woggon U, Owschimikow N, Li X. Phonon-Assisted Intervalley Scattering Determines Ultrafast Exciton Dynamics in MoSe_{2} Bilayers. PHYSICAL REVIEW LETTERS 2021; 127:157403. [PMID: 34678033 DOI: 10.1103/physrevlett.127.157403] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 04/23/2021] [Accepted: 08/23/2021] [Indexed: 06/13/2023]
Abstract
While valleys (energy extrema) are present in all band structures of solids, their preeminent role in determining exciton resonances and dynamics in atomically thin transition metal dichalcogenides (TMDC) is unique. Using two-dimensional coherent electronic spectroscopy, we find that exciton decoherence occurs on a much faster timescale in MoSe_{2} bilayers than that in the monolayers. We further identify two population relaxation channels in the bilayer, a coherent and an incoherent one. Our microscopic model reveals that phonon-emission processes facilitate scattering events from the K valley to other lower-energy Γ and Λ valleys in the bilayer. Our combined experimental and theoretical studies unequivocally establish different microscopic mechanisms that determine exciton quantum dynamics in TMDC monolayers and bilayers. Understanding exciton quantum dynamics provides critical guidance to the manipulation of spin-valley degrees of freedom in TMDC bilayers.
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Affiliation(s)
- Sophia Helmrich
- Department of Optics and Atomic Physics, Technical University Berlin, Berlin 10623, Germany
| | - Kevin Sampson
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
- Center for Dynamics and Control of Materials and Texas Materials Institute, 2501 Speedway, Austin, Texas 78712, USA
| | - Di Huang
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Malte Selig
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
| | - Kai Hao
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Kha Tran
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Alexander Achstein
- Department of Optics and Atomic Physics, Technical University Berlin, Berlin 10623, Germany
| | - Carter Young
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Andreas Knorr
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
| | - Ermin Malic
- Department of Physics, Philipps University Marburg, 35037 Marburg, Germany
| | - Ulrike Woggon
- Department of Optics and Atomic Physics, Technical University Berlin, Berlin 10623, Germany
| | - Nina Owschimikow
- Department of Optics and Atomic Physics, Technical University Berlin, Berlin 10623, Germany
| | - Xiaoqin Li
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
- Center for Dynamics and Control of Materials and Texas Materials Institute, 2501 Speedway, Austin, Texas 78712, USA
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44
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Li E, Hu JX, Feng X, Zhou Z, An L, Law KT, Wang N, Lin N. Lattice reconstruction induced multiple ultra-flat bands in twisted bilayer WSe 2. Nat Commun 2021; 12:5601. [PMID: 34556663 PMCID: PMC8460827 DOI: 10.1038/s41467-021-25924-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 08/31/2021] [Indexed: 12/05/2022] Open
Abstract
Moiré superlattices in van der Waals heterostructures provide a tunable platform to study emergent properties that are absent in the natural crystal form. Twisted bilayer transition metal dichalcogenides (TB-TMDs) can host moiré flat bands over a wide range of twist angles. For twist angle close to 60°, it was predicted that TB-TMDs undergo a lattice reconstruction which causes the formation of ultra-flat bands. Here, by using scanning tunneling microscopy and spectroscopy, we show the emergence of multiple ultra-flat bands in twisted bilayer WSe2 when the twist angle is within 3° of 60°. The ultra-flat bands are manifested as narrow tunneling conductance peaks with estimated bandwidth less than 10 meV, which is only a fraction of the estimated on-site Coulomb repulsion energy. The number of these ultra-flat bands and spatial distribution of the wavefunctions match well with the theoretical predictions, strongly evidencing that the observed ultra-flat bands are induced by lattice reconstruction. Our work provides a foundation for further study of the exotic correlated phases in TB-TMDs. It was predicted that lattice reconstruction can lead to the emergence of multiple ultra-flat electronic bands in twisted bilayer transition metal dichalcogenides. Here, by using scanning tunneling microscopy and spectroscopy, the authors demonstrate such bands in twisted bilayer WSe2.
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Affiliation(s)
- En Li
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Jin-Xin Hu
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Xuemeng Feng
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Zishu Zhou
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Liheng An
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Kam Tuen Law
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China.
| | - Ning Wang
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China.
| | - Nian Lin
- Department of Physics, The Hong Kong University of Science and Technology, Hong Kong SAR, China.
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45
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Wu K, Zhong H, Guo Q, Tang J, Zhang J, Qian L, Shi Z, Zhang C, Yuan S, Zhang S, Xu H. Identification of twist-angle-dependent excitons in WS2/WSe2 heterobilayers. Natl Sci Rev 2021; 9:nwab135. [PMID: 35795458 PMCID: PMC9252742 DOI: 10.1093/nsr/nwab135] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 06/30/2021] [Accepted: 07/12/2021] [Indexed: 11/13/2022] Open
Abstract
Abstract
Stacking atomically thin films enables artificial construction of van der Waals heterostructures with exotic functionalities such as superconductivity, the quantum Hall effect, and engineered light-matter interactions. In particular, heterobilayers composed of monolayer transition metal dichalcogenides have attracted significant interest due to their controllable interlayer coupling and trapped valley excitons in moiré superlattices. However, the identification of twist-angle-modulated optical transitions in heterobilayers is sometimes controversial since both momentum-direct (K-K) and -indirect excitons reside on the low energy side of the bright exciton in the monolayer constituents. Here, we attribute the optical transition at approximately 1.35 eV in the WS2/WSe2 heterobilayer to an indirect Γ-K transition based on a systematic analysis and comparison of experimental PL spectra with theoretical calculations. The exciton wavefunction obtained by the state-of-the-art GW-Bethe-Salpeter equation (GW-BSE) approach indicates that both the electron and hole of the exciton are contributed by the WS2 layer. Polarization-resolved k-space imaging further confirms that the transition dipole moment of this optical transition is dominantly in-plane and is independent of the twist angle. The calculated absorption spectrum predicts that the usually called interlayer exciton peak coming from the K-K transition is located at 1.06 eV, but with a much weaker amplitude. Our work provides new insights into understanding the steady-state and dynamic properties of twist-angle-dependent excitons in van der Waals heterostructures.
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Affiliation(s)
- Ke Wu
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Hongxia Zhong
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Quanbing Guo
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Jibo Tang
- The Institute for Advanced Studies, Wuhan University, Wuhan 430072, China
| | - Jing Zhang
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Lihua Qian
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhifeng Shi
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, China
| | - Chendong Zhang
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Shengjun Yuan
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Shunping Zhang
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Hongxing Xu
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
- The Institute for Advanced Studies, Wuhan University, Wuhan 430072, China
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46
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Bilayer Wigner crystals in a transition metal dichalcogenide heterostructure. Nature 2021; 595:48-52. [PMID: 34194017 DOI: 10.1038/s41586-021-03560-w] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Accepted: 04/15/2021] [Indexed: 02/06/2023]
Abstract
One of the first theoretically predicted manifestations of strong interactions in many-electron systems was the Wigner crystal1-3, in which electrons crystallize into a regular lattice. The crystal can melt via either thermal or quantum fluctuations4. Quantum melting of the Wigner crystal is predicted to produce exotic intermediate phases5,6 and quantum magnetism7,8 because of the intricate interplay of Coulomb interactions and kinetic energy. However, studying two-dimensional Wigner crystals in the quantum regime has often required a strong magnetic field9-11 or a moiré superlattice potential12-15, thus limiting access to the full phase diagram of the interacting electron liquid. Here we report the observation of bilayer Wigner crystals without magnetic fields or moiré potentials in an atomically thin transition metal dichalcogenide heterostructure, which consists of two MoSe2 monolayers separated by hexagonal boron nitride. We observe optical signatures of robust correlated insulating states at symmetric (1:1) and asymmetric (3:1, 4:1 and 7:1) electron doping of the two MoSe2 layers at cryogenic temperatures. We attribute these features to bilayer Wigner crystals composed of two interlocked commensurate triangular electron lattices, stabilized by inter-layer interaction16. The Wigner crystal phases are remarkably stable, and undergo quantum and thermal melting transitions at electron densities of up to 6 × 1012 per square centimetre and at temperatures of up to about 40 kelvin. Our results demonstrate that an atomically thin heterostructure is a highly tunable platform for realizing many-body electronic states and probing their liquid-solid and magnetic quantum phase transitions4-8,17.
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47
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Weak ferroelectric charge transfer in layer-asymmetric bilayers of 2D semiconductors. Sci Rep 2021; 11:13422. [PMID: 34183714 PMCID: PMC8239035 DOI: 10.1038/s41598-021-92710-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 05/31/2021] [Indexed: 11/13/2022] Open
Abstract
In bilayers of two-dimensional semiconductors with stacking arrangements which lack inversion symmetry charge transfer between the layers due to layer-asymmetric interband hybridisation can generate a potential difference between the layers. We analyse bilayers of transition metal dichalcogenides (TMDs)—in particular, \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {WSe}_2$$\end{document}WSe2—for which we find a substantial stacking-dependent charge transfer, and InSe, for which the charge transfer is found to be negligibly small. The information obtained about TMDs is then used to map potentials generated by the interlayer charge transfer across the moiré superlattice in twistronic bilayers.
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48
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Vizner Stern M, Waschitz Y, Cao W, Nevo I, Watanabe K, Taniguchi T, Sela E, Urbakh M, Hod O, Ben Shalom M. Interfacial ferroelectricity by van der Waals sliding. Science 2021; 372:eabe8177. [PMID: 34112727 DOI: 10.1126/science.abe8177] [Citation(s) in RCA: 154] [Impact Index Per Article: 51.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 05/10/2021] [Indexed: 12/14/2022]
Abstract
Despite their partial ionic nature, many layered diatomic crystals avoid internal electric polarization by forming a centrosymmetric lattice at their optimal van-der-Waals stacking. Here, we report a stable ferroelectric order emerging at the interface between two naturally-grown flakes of hexagonal-boron-nitride, which are stacked together in a metastable non-centrosymmetric parallel orientation. We observe alternating domains of inverted normal polarization, caused by a lateral shift of one lattice site between the domains. Reversible polarization switching coupled to lateral sliding is achieved by scanning a biased tip above the surface. Our calculations trace the origin of the phenomenon to a subtle interplay between charge redistribution and ionic displacement, and provide intuitive insights to explore the interfacial polarization and its unique "slidetronics" switching mechanism.
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Affiliation(s)
- M Vizner Stern
- School of Physics and Astronomy, Tel Aviv University, Israel
| | - Y Waschitz
- School of Physics and Astronomy, Tel Aviv University, Israel
| | - W Cao
- Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 6997801, Israel
| | - I Nevo
- School of Physics and Astronomy, Tel Aviv University, Israel
| | - K Watanabe
- National Institute for Material Science, Tsukuba, Japan
| | - T Taniguchi
- National Institute for Material Science, Tsukuba, Japan
| | - E Sela
- School of Physics and Astronomy, Tel Aviv University, Israel
| | - M Urbakh
- Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 6997801, Israel
| | - O Hod
- Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences and The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 6997801, Israel
| | - M Ben Shalom
- School of Physics and Astronomy, Tel Aviv University, Israel.
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Liu Y, Zeng C, Yu J, Zhong J, Li B, Zhang Z, Liu Z, Wang ZM, Pan A, Duan X. Moiré superlattices and related moiré excitons in twisted van der Waals heterostructures. Chem Soc Rev 2021; 50:6401-6422. [PMID: 33942837 DOI: 10.1039/d0cs01002b] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Recent advances in moiré superlattices and moiré excitons, such as quantum emission arrays, low-energy flat bands, and Mott insulators, have rapidly attracted attention in the fields of optoelectronics, materials, and energy research. The interlayer twist turns into a degree of freedom that alters the properties of the systems of materials, and the realization of moiré excitons also offers the feasibility of making artificial exciton crystals. Moreover, moiré excitons exhibit many exciting properties under the regulation of various external conditions, including spatial polarisation, alternating dipolar to alternating dipolar moments and gate-dependence to gate voltage dependence; all are pertinent to their applications in nano-photonics and quantum information. But the lag in theoretical development and the low-efficiency of processing technologies significantly limit the potential of moiré superlattice applications. In this review, we systematically summarise and discuss the recent progress in moiré superlattices and moiré excitons, and analyze the current challenges, and put forward relevant recommendations. There is no doubt that further research will lead to breakthroughs in their application and promote reforms and innovations in traditional solid-state physics and materials science.
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Affiliation(s)
- Yanping Liu
- School of Physics and Electronics, Hunan Key Laboratory for Super-microstructure and Ultrafast Process, Central South University, 932 South Lushan Road, Changsha, Hunan 410083, People's Republic of China.
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Yasuda K, Wang X, Watanabe K, Taniguchi T, Jarillo-Herrero P. Stacking-engineered ferroelectricity in bilayer boron nitride. Science 2021; 372:eabd3230. [PMID: 34045323 DOI: 10.1126/science.abd3230] [Citation(s) in RCA: 186] [Impact Index Per Article: 62.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 05/07/2021] [Indexed: 02/24/2024]
Abstract
2D ferroelectrics with robust polarization down to atomic thicknesses provide building blocks for functional heterostructures. Experimental realization remains challenging because of the requirement of a layered polar crystal. Here, we demonstrate a rational design approach to engineering 2D ferroelectrics from a non-ferroelectric parent compound via employing van der Waals assembly. Parallel-stacked bilayer boron nitride exhibits out-of-plane electric polarization that reverses depending on the stacking order. The polarization switching is probed via the resistance of an adjacently stacked graphene sheet. Twisting the boron nitride sheets by a small angle changes the dynamics of switching thanks to the formation of moiré ferroelectricity with staggered polarization. The ferroelectricity persists to room temperature while keeping the high mobility of graphene, paving the way for potential ultrathin nonvolatile memory applications.
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Affiliation(s)
- Kenji Yasuda
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| | - Xirui Wang
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Pablo Jarillo-Herrero
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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