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Lee S, Jin KH, Jung H, Fukutani K, Lee J, Kwon CI, Kim JS, Kim J, Yeom HW. Surface Doping and Dual Nature of the Band Gap in Excitonic Insulator Ta 2NiSe 5. ACS NANO 2024; 18:24784-24791. [PMID: 39178330 PMCID: PMC11394347 DOI: 10.1021/acsnano.4c02784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2024]
Abstract
Excitons in semiconductors and molecules are widely utilized in photovoltaics and optoelectronics, and high-temperature coherent quantum states of excitons can be realized in artificial electron-hole bilayers and an exotic material of an excitonic insulator (EI). Here, we investigate the band gap evolution of a putative high-temperature EI Ta2NiSe5 upon surface doing by alkali adsorbates with angle-resolved photoemission and density functional theory (DFT) calculations. The conduction band of Ta2NiSe5 is filled by the charge transfer from alkali adsorbates, and the band gap decreases drastically upon the increase of metallic electron density. Our DFT calculation, however, reveals that there exist both structural and excitonic contributions to the band gap tuned. While electron doping reduces the band gap substantially, it alone is not enough to close the band gap. In contrast, the structural distortion induced by the alkali adsorbate plays a critical role in the gap closure. This work indicates a combined electronic and structural nature for the EI phase of the present system and the complexity of surface doping beyond charge transfer.
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Affiliation(s)
- Siwon Lee
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Kyung-Hwan Jin
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics and Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Hyunjin Jung
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Keisuke Fukutani
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
| | - Jinwon Lee
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft 2628 CJ, The Netherlands
| | - Chang Il Kwon
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Jun Sung Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Jaeyoung Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
| | - Han Woong Yeom
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
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2
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Hwang J, Ruan W, Chen Y, Tang S, Crommie MF, Shen ZX, Mo SK. Charge density waves in two-dimensional transition metal dichalcogenides. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2024; 87:044502. [PMID: 38518359 DOI: 10.1088/1361-6633/ad36d3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 03/22/2024] [Indexed: 03/24/2024]
Abstract
Charge density wave (CDW is one of the most ubiquitous electronic orders in quantum materials. While the essential ingredients of CDW order have been extensively studied, a comprehensive microscopic understanding is yet to be reached. Recent research efforts on the CDW phenomena in two-dimensional (2D) materials provide a new pathway toward a deeper understanding of its complexity. This review provides an overview of the CDW orders in 2D with atomically thin transition metal dichalcogenides (TMDCs) as the materials platform. We mainly focus on the electronic structure investigations on the epitaxially grown TMDC samples with angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy as complementary experimental tools. We discuss the possible origins of the 2D CDW, novel quantum states coexisting with them, and exotic types of charge orders that can only be realized in the 2D limit.
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Affiliation(s)
- Jinwoong Hwang
- Department of Physics and Institute of Quantum Convergence Technology, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Wei Ruan
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, People's Republic of China
| | - Yi Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing 100871, People's Republic of China
| | - Shujie Tang
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, People's Republic of China
| | - Michael F Crommie
- Department of Physics, University of California, Berkeley, CA, United States of America
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States of America
- Kavli Energy NanoSciences Institute at the University of California at Berkeley, Berkeley, CA 94720, United States of America
| | - Zhi-Xun Shen
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA, United States of America
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, United States of America
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 United States of America
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Que Y, Chan YH, Jia J, Das A, Tong Z, Chang YT, Cui Z, Kumar A, Singh G, Mukherjee S, Lin H, Weber B. A Gate-Tunable Ambipolar Quantum Phase Transition in a Topological Excitonic Insulator. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2309356. [PMID: 38010877 DOI: 10.1002/adma.202309356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/26/2023] [Indexed: 11/29/2023]
Abstract
Coulomb interactions among electrons and holes in 2D semimetals with overlapping valence and conduction bands can give rise to a correlated insulating ground state via exciton formation and condensation. One candidate material in which such excitonic state uniquely combines with non-trivial band topology are atomic monolayers of tungsten ditelluride (WTe2 ), in which a 2D topological excitonic insulator (2D TEI) forms. However, the detailed mechanism of the 2D bulk gap formation in WTe2 , in particular with regard to the role of Coulomb interactions, has remained a subject of ongoing debate. Here, it shows that WTe2 is susceptible to a gate-tunable quantum phase transition, evident from an abrupt collapse of its 2D bulk energy gap upon ambipolar field-effect doping. Such gate tunability of a 2D TEI, into either n- and p-type semimetals, promises novel handles of control over non-trivial 2D superconductivity with excitonic pairing.
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Affiliation(s)
- Yande Que
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Yang-Hao Chan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 106319, Taiwan
- Physics Division, National Center of Theoretical Physics, Taipei, 10617, Taiwan
| | - Junxiang Jia
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Anirban Das
- Department of Physics, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
- Center for Atomistic Modelling and Materials Design, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
| | - Zhengjue Tong
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Yu-Tzu Chang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 106319, Taiwan
| | - Zhenhao Cui
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Amit Kumar
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Gagandeep Singh
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Shantanu Mukherjee
- Department of Physics, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
- Center for Atomistic Modelling and Materials Design, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
- Quantum Centre for Diamond and Emergent Materials, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
| | - Hsin Lin
- Institute of Physics, Academia Sinica, Taipei, 115201, Taiwan
| | - Bent Weber
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
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Chin HT, Wang DC, Gulo DP, Yao YC, Yeh HC, Muthu J, Chen DR, Kao TC, Kalbáč M, Lin PH, Cheng CM, Hofmann M, Liang CT, Liu HL, Chuang FC, Hsieh YP. Tungsten Nitride (W 5N 6): An Ultraresilient 2D Semimetal. NANO LETTERS 2024; 24:67-73. [PMID: 38149785 DOI: 10.1021/acs.nanolett.3c03243] [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
Two-dimensional transition metal nitrides offer intriguing possibilities for achieving novel electronic and mechanical functionality owing to their distinctive and tunable bonding characteristics compared to other 2D materials. We demonstrate here the enabling effects of strong bonding on the morphology and functionality of 2D tungsten nitrides. The employed bottom-up synthesis experienced a unique substrate stabilization effect beyond van-der-Waals epitaxy that favored W5N6 over lower metal nitrides. Comprehensive structural and electronic characterization reveals that monolayer W5N6 can be synthesized at large scale and shows semimetallic behavior with an intriguing indirect band structure. Moreover, the material exhibits exceptional resilience against mechanical damage and chemical reactions. Leveraging these electronic properties and robustness, we demonstrate the application of W5N6 as atomic-scale dry etch stops that allow the integration of high-performance 2D materials contacts. These findings highlight the potential of 2D transition metal nitrides for realizing advanced electronic devices and functional interfaces.
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Affiliation(s)
- Hao-Ting Chin
- Molecular Science and Technology Program, Taiwan International Graduate Program, Academia Sinica, Taipei 10617, Taiwan
- International Graduate Program of Molecular Science and Technology, National Taiwan University, Taipei 10617, Taiwan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Deng-Chi Wang
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
| | | | - Yu-Chi Yao
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Hao-Chen Yeh
- Institute of Physics, Academia Sinica, Taipei 115201, Taiwan
| | - Jeyavelan Muthu
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
- International Graduate Program of Nano Science and Technology, National Taiwan University, Taipei 10617, Taiwan
| | - Ding-Rui Chen
- Molecular Science and Technology Program, Taiwan International Graduate Program, Academia Sinica, Taipei 10617, Taiwan
- International Graduate Program of Molecular Science and Technology, National Taiwan University, Taipei 10617, Taiwan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Tzu-Chun Kao
- Graduate Institute of Applied Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Martin Kalbáč
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague, Czech Republic
| | - Ping-Hui Lin
- National Synchrotron Radiation Research Center (NSRRC), Hsinchu 300092, Taiwan
| | - Cheng-Maw Cheng
- National Synchrotron Radiation Research Center (NSRRC), Hsinchu 300092, Taiwan
| | - Mario Hofmann
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Chi-Te Liang
- Department of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Hsiang-Lin Liu
- Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan
| | - Feng-Chuan Chuang
- Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
- Center for Theoretical and Computational Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Ya-Ping Hsieh
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
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Antonelli T, Rajan A, Watson MD, Soltani S, Houghton J, Siemann GR, Zivanovic A, Bigi C, Edwards B, King PDC. Controlling the Charge Density Wave Transition in Single-Layer TiTe 2xSe 2(1-x) Alloys by Band Gap Engineering. NANO LETTERS 2024; 24:215-221. [PMID: 38117702 PMCID: PMC10786161 DOI: 10.1021/acs.nanolett.3c03776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 12/13/2023] [Accepted: 12/14/2023] [Indexed: 12/22/2023]
Abstract
Closing the band gap of a semiconductor into a semimetallic state gives a powerful potential route to tune the electronic energy gains that drive collective phases like charge density waves (CDWs) and excitonic insulator states. We explore this approach for the controversial CDW material monolayer (ML) TiSe2 by engineering its narrow band gap to the semimetallic limit of ML-TiTe2. Using molecular beam epitaxy, we demonstrate the growth of ML-TiTe2xSe2(1-x) alloys across the entire compositional range and unveil how the (2 × 2) CDW instability evolves through the normal state semiconductor-semimetal transition via in situ angle-resolved photoemission spectroscopy. Through model electronic structure calculations, we identify how this tunes the relative strength of excitonic and Peierls-like coupling, demonstrating band gap engineering as a powerful method for controlling the microscopic mechanisms underpinning the formation of collective states in two-dimensional materials.
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Affiliation(s)
- Tommaso Antonelli
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Akhil Rajan
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Matthew D. Watson
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | | | - Joe Houghton
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Gesa-Roxanne Siemann
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Andela Zivanovic
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Chiara Bigi
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Brendan Edwards
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Phil D. C. King
- SUPA, School of Physics and
AstronomyUniversity of St Andrews, St Andrews KY16 9SS, United Kingdom
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6
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Wen X, Lei W, Li X, Di B, Zhou Y, Zhang J, Zhang Y, Li L, Chang H, Zhang W. ZrTe 2 Compound Dirac Semimetal Contacts for High-Performance MoS 2 Transistors. NANO LETTERS 2023; 23:8419-8425. [PMID: 37708326 DOI: 10.1021/acs.nanolett.3c01554] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/16/2023]
Abstract
Recent investigations reveal elemental semimetal (Bi and Sb) contacts fabricated with conventional deposition processes exhibit a remarkable capacity of approaching the quantum limit in two-dimensional (2D) semiconductor contacts, implying it might be an optimal option to solve the contact issue of 2D semiconductor electronics. Here, we demonstrate novel compound Dirac semimetal ZrTe2 contacts to MoS2 constructed by a nondestructive van der Waals (vdW) transfer process, exhibiting excellent ohmic contact characteristics with a negligible Schottky barrier. The band hybridization between ZrTe2 and MoS2 was verified. The bilayer MoS2 transistor with a 250 nm channel length on a 20 nm thick hexagonal boron nitride (h-BN) exhibits an ION/IOFF current ratio over 105 and an on-state current of 259 μA μm-1. The current results reveal that 2D compound semimetals with vdW contacts can offer a diverse selection of proper semimetals with adjustable work functions for the next-generation 2D-based beyond-silicon electronics.
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Affiliation(s)
- Xiaokun Wen
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
- Shenzhen R&D Center of Huazhong University of Science and Technology, Shenzhen 518000, People's Republic of China
| | - Wenyu Lei
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
- Shenzhen R&D Center of Huazhong University of Science and Technology, Shenzhen 518000, People's Republic of China
| | - Xinlu Li
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China
| | - Boyuan Di
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
- Shenzhen R&D Center of Huazhong University of Science and Technology, Shenzhen 518000, People's Republic of China
| | - Ye Zhou
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China
| | - Jia Zhang
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China
| | - Yuhui Zhang
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
- Shenzhen R&D Center of Huazhong University of Science and Technology, Shenzhen 518000, People's Republic of China
| | - Liufan Li
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
- Shenzhen R&D Center of Huazhong University of Science and Technology, Shenzhen 518000, People's Republic of China
| | - Haixin Chang
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
- Shenzhen R&D Center of Huazhong University of Science and Technology, Shenzhen 518000, People's Republic of China
| | - Wenfeng Zhang
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
- Shenzhen R&D Center of Huazhong University of Science and Technology, Shenzhen 518000, People's Republic of China
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