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Bhowmik S, Ghosh A, Chandni U. Emergent phases in graphene flat bands. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2024; 87:096401. [PMID: 39059412 DOI: 10.1088/1361-6633/ad67ed] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 07/26/2024] [Indexed: 07/28/2024]
Abstract
Electronic correlations in two-dimensional materials play a crucial role in stabilising emergent phases of matter. The realisation of correlation-driven phenomena in graphene has remained a longstanding goal, primarily due to the absence of strong electron-electron interactions within its low-energy bands. In this context, magic-angle twisted bilayer graphene has recently emerged as a novel platform featuring correlated phases favoured by the low-energy flat bands of the underlying moiré superlattice. Notably, the observation of correlated insulators and superconductivity, and the interplay between these phases have garnered significant attention. A wealth of correlated phases with unprecedented tunability was discovered subsequently, including orbital ferromagnetism, Chern insulators, strange metallicity, density waves, and nematicity. However, a comprehensive understanding of these closely competing phases remains elusive. The ability to controllably twist and stack multiple graphene layers has enabled the creation of a whole new family of moiré superlattices with myriad properties. Here, we review the progress and development achieved so far, encompassing the rich phase diagrams offered by these graphene-based moiré systems. Additionally, we discuss multiple phases recently observed in non-moiré multilayer graphene systems. Finally, we outline future opportunities and challenges for the exploration of hidden phases in this new generation of moiré materials.
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Affiliation(s)
- Saisab Bhowmik
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India
| | - Arindam Ghosh
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore 560012, India
| | - U Chandni
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India
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2
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Srivastava PK, Hassan Y, Lee S, Joe M, Abbas MS, Ahn H, Tiwari A, Ghosh S, Yoo WJ, Singh B, Low T, Lee C. Unusual Dzyaloshinskii-Moriya Interaction in Graphene/Fe 3GeTe 2 Van der Waals Heterostructure. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2402604. [PMID: 38898739 DOI: 10.1002/smll.202402604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Revised: 05/18/2024] [Indexed: 06/21/2024]
Abstract
Dzyaloshinskii-Moriya interaction (DMI) is shown to induce a topologically protected chiral spin texture in magnetic/nonmagnetic heterostructures. In the context of van der Waals spintronic devices, graphene emerges as an excellent candidate material. However, due to its negligible spin-orbit interaction, inducing DMI to stabilize topological spins when coupled to 3d-ferromagnets remains challenging. Here, it is demonstrated that, despite these challenges, a sizeable Rashba-type spin splitting followed by significant DMI is induced in graphene/Fe3GeTe2. This is made possible due to an interfacial electric field driven by charge asymmetry together with the broken inversion symmetry of the heterostructure. These findings reveal that the enhanced DMI energy parameter, resulting from a large effective electron mass in Fe3GeTe2, remarkably contributes to stabilizing non-collinear spins below the Curie temperature, overcoming the magnetic anisotropy energy. These results are supported by the topological Hall effect, which coexists with the non-trivial breakdown of Fermi liquid behavior, confirming the interplay between spins and non-trivial topology. This work paves the way toward the design and control of interface-driven skyrmion-based devices.
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Affiliation(s)
| | - Yasir Hassan
- Department of Materials Science and Engineering, Chungnam National University, 99, Daehak-ro, Yuseong-gu, Daejeon, 34143, South Korea
| | - Seungjun Lee
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, 55455, USA
| | - Minwoong Joe
- School of Mechanical Engineering, Sungkyunkwan University, Suwon, 16419, South Korea
- Department of Materials Science and Engineering, Chungnam National University, 99, Daehak-ro, Yuseong-gu, Daejeon, 34143, South Korea
| | - Muhammad Sabbtain Abbas
- Centre for Advanced Studies in Physics, Government College University Lahore, Lahore, 54000, Pakistan
| | - Hyobin Ahn
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, South Korea
| | - Ankita Tiwari
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Subhasis Ghosh
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Won Jong Yoo
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, South Korea
| | - Budhi Singh
- School of Mechanical Engineering, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Tony Low
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, 55455, USA
| | - Changgu Lee
- School of Mechanical Engineering, Sungkyunkwan University, Suwon, 16419, South Korea
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, South Korea
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3
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Jeong J, Kiem DH, Guo D, Duan R, Watanabe K, Taniguchi T, Liu Z, Han MJ, Zheng S, Yang H. Spin-Selective Memtransistors with Magnetized Graphene. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2310291. [PMID: 38235929 DOI: 10.1002/adma.202310291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 12/08/2023] [Indexed: 01/19/2024]
Abstract
Spin-polarized bands in pristine and proximity-induced magnetic materials are promising building blocks for future devices. Conceptually new memory, logic, and neuromorphic devices are conceived based on atomically thin magnetic materials and the manipulation of their spin-polarized bands via electrical and optical methods. A critical remaining issue is the direct probe and the optimized use of the magnetic coupling effect in van der Waals heterostructures, which requires further delicate design of atomically thin magnetic materials and devices. Here, a spin-selective memtransistor with magnetized single-layered graphene on a reactive antiferromagnetic material, CrI3, is reported. The spin-dependent hybridization between graphene and CrI3 atomic layers enables the spin-selective bandgap opening in the single-layered graphene and the electric field control of magnetization in a specific CrI3 layer. The microscopic working principle is clarified by the first-principles calculations and theoretical analysis of the transport data. Reliable memtransistor operations (i.e., memory and logic device-combined operations), as well as a spin-selective probe of Landau levels in the magnetized graphene, are achieved by using the subtle manipulation of the magnetic proximity effect via electrical means.
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Affiliation(s)
- Juyeong Jeong
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
| | - Do Hoon Kiem
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
| | - Dan Guo
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Ruihuan Duan
- CINTRA CNRS/NTU/THALES, Research Techno Plaza, Nanyang Technological University, Singapore, 637371, Singapore
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore
| | - Kenji Watanabe
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 3030044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 3030044, Japan
| | - Zheng Liu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore
| | - Myung Joon Han
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
| | - Shoujun Zheng
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Heejun Yang
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
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4
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Wu H, Yang L, Zhang G, Jin W, Xiao B, Zhang W, Chang H. Robust Magnetic Proximity Induced Anomalous Hall Effect in a Room Temperature van der Waals Ferromagnetic Semiconductor Based 2D Heterostructure. SMALL METHODS 2024:e2301524. [PMID: 38295050 DOI: 10.1002/smtd.202301524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 01/04/2024] [Indexed: 02/02/2024]
Abstract
Developing novel high-temperature van der Waals ferromagnetic semiconductor materials and investigating their interface coupling effects with 2D topological semimetals are pivotal for advancing next-generation spintronic and quantum devices. However, most van der Waals ferromagnetic semiconductors exhibit ferromagnetism only at low temperatures, limiting the proximity research on their interfaces with topological semimetals. Here, an intrinsic, van der Waals layered room-temperature ferromagnetic semiconductor crystal, FeCr0.5 Ga1.5 Se4 (FCGS), is reported with a Curie temperature (TC ) as high as 370 K, setting a new record for van der Waals ferromagnetic semiconductors. The saturation magnetization at low temperature (2 K) and room temperature (300 K) reaches 8.2 and 2.7 emu g-1 , respectively. Furthermore, FCGS possesses a bandgap of ≈1.2 eV, which is comparable to the widely used commercial silicon. The FCGS/graphene 2D heterostructure exhibits an impeccably smooth and gapless interface, thereby inducing a robust van der Waals magnetic proximity coupling effect between FCGS and graphene. After the proximity coupling, graphene undergoes a charge carrier transition from electrons to holes, accompanied by a transition from non-magnetic to ferromagnetic transport behavior with robust anomalous Hall effect (AHE). Notably, the van der Waals magnetic proximity-induced AHE remains robust even up to 400 K.
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Affiliation(s)
- Hao Wu
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
- Institute for Quantum Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Li Yang
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Gaojie Zhang
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
- Institute for Quantum Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
- Shenzhen R&D Center of Huazhong University of Science and Technology (HUST), Shenzhen, 518000, China
| | - Wen Jin
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Bichen Xiao
- Center for Joining and Electronic Packaging, State Key Laboratory of Material Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, 430074, China
| | - Wenfeng Zhang
- Shenzhen R&D Center of Huazhong University of Science and Technology (HUST), Shenzhen, 518000, China
| | - Haixin Chang
- Shenzhen R&D Center of Huazhong University of Science and Technology (HUST), Shenzhen, 518000, China
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5
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Dapolito M, Tsuneto M, Zheng W, Wehmeier L, Xu S, Chen X, Sun J, Du Z, Shao Y, Jing R, Zhang S, Bercher A, Dong Y, Halbertal D, Ravindran V, Zhou Z, Petrovic M, Gozar A, Carr GL, Li Q, Kuzmenko AB, Fogler MM, Basov DN, Du X, Liu M. Infrared nano-imaging of Dirac magnetoexcitons in graphene. NATURE NANOTECHNOLOGY 2023; 18:1409-1415. [PMID: 37605044 DOI: 10.1038/s41565-023-01488-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 07/17/2023] [Indexed: 08/23/2023]
Abstract
Magnetic fields can have profound effects on the motion of electrons in quantum materials. Two-dimensional electron systems subject to strong magnetic fields are expected to exhibit quantized Hall conductivity, chiral edge currents and distinctive collective modes referred to as magnetoplasmons and magnetoexcitons. Generating these propagating collective modes in charge-neutral samples and imaging them at their native nanometre length scales have thus far been experimentally elusive. Here we visualize propagating magnetoexciton polaritons at their native length scales and report their magnetic-field-tunable dispersion in near-charge-neutral graphene. Imaging these collective modes and their associated nano-electro-optical responses allows us to identify polariton-modulated optical and photo-thermal electric effects at the sample edges, which are the most pronounced near charge neutrality. Our work is enabled by innovations in cryogenic near-field optical microscopy techniques that allow for the nano-imaging of the near-field responses of two-dimensional materials under magnetic fields up to 7 T. This nano-magneto-optics approach allows us to explore and manipulate magnetopolaritons in specimens with low carrier doping via harnessing high magnetic fields.
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Affiliation(s)
- Michael Dapolito
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
- Department of Physics, Columbia University, New York, NY, USA
| | - Makoto Tsuneto
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - Wenjun Zheng
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - Lukas Wehmeier
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA
| | - Suheng Xu
- Department of Physics, Columbia University, New York, NY, USA
| | - Xinzhong Chen
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
- Department of Physics, Columbia University, New York, NY, USA
| | - Jiacheng Sun
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - Zengyi Du
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - Yinming Shao
- Department of Physics, Columbia University, New York, NY, USA
| | - Ran Jing
- Department of Physics, Columbia University, New York, NY, USA
| | - Shuai Zhang
- Department of Physics, Columbia University, New York, NY, USA
| | - Adrien Bercher
- Département de Physique de la Matière Quantique, Université de Genève, Genève 4, Switzerland
| | - Yinan Dong
- Department of Physics, Columbia University, New York, NY, USA
| | - Dorri Halbertal
- Department of Physics, Columbia University, New York, NY, USA
| | - Vibhu Ravindran
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
- Department of Physics, University of California, Berkeley, CA, USA
| | - Zijian Zhou
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - Mila Petrovic
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
| | - Adrian Gozar
- Department of Physics, Yale University, New Haven, CT, USA
- Energy Sciences Institute, Yale University, West Haven, CT, USA
| | - G L Carr
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA
| | - Qiang Li
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, USA
| | - Alexey B Kuzmenko
- Département de Physique de la Matière Quantique, Université de Genève, Genève 4, Switzerland
| | - Michael M Fogler
- Department of Physics, University of California at San Diego, La Jolla, CA, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, USA.
| | - Xu Du
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA.
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA.
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA.
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6
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Kim D, Pandey J, Jeong J, Cho W, Lee S, Cho S, Yang H. Phase Engineering of 2D Materials. Chem Rev 2023; 123:11230-11268. [PMID: 37589590 DOI: 10.1021/acs.chemrev.3c00132] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/18/2023]
Abstract
Polymorphic 2D materials allow structural and electronic phase engineering, which can be used to realize energy-efficient, cost-effective, and scalable device applications. The phase engineering covers not only conventional structural and metal-insulator transitions but also magnetic states, strongly correlated band structures, and topological phases in rich 2D materials. The methods used for the local phase engineering of 2D materials include various optical, geometrical, and chemical processes as well as traditional thermodynamic approaches. In this Review, we survey the precise manipulation of local phases and phase patterning of 2D materials, particularly with ideal and versatile phase interfaces for electronic and energy device applications. Polymorphic 2D materials and diverse quantum materials with their layered, vertical, and lateral geometries are discussed with an emphasis on the role and use of their phase interfaces. Various phase interfaces have demonstrated superior and unique performance in electronic and energy devices. The phase patterning leads to novel homo- and heterojunction structures of 2D materials with low-dimensional phase boundaries, which highlights their potential for technological breakthroughs in future electronic, quantum, and energy devices. Accordingly, we encourage researchers to investigate and exploit phase patterning in emerging 2D materials.
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Affiliation(s)
- Dohyun Kim
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Juhi Pandey
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Juyeong Jeong
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Woohyun Cho
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Seungyeon Lee
- Division of Chemical Engineering and Materials Science, Graduate Program in System Health Science and Engineering, Ewha Womans University, Seoul 03760, Korea
| | - Suyeon Cho
- Division of Chemical Engineering and Materials Science, Graduate Program in System Health Science and Engineering, Ewha Womans University, Seoul 03760, Korea
| | - Heejun Yang
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
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7
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Lu X, Zhang S, Wang Y, Gao X, Yang K, Guo Z, Gao Y, Ye Y, Han Z, Liu J. Synergistic correlated states and nontrivial topology in coupled graphene-insulator heterostructures. Nat Commun 2023; 14:5550. [PMID: 37689704 PMCID: PMC10492827 DOI: 10.1038/s41467-023-41293-8] [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: 02/28/2023] [Accepted: 08/29/2023] [Indexed: 09/11/2023] Open
Abstract
Graphene has aroused great attention due to the intriguing properties associated with its low-energy Dirac Hamiltonian. When graphene is coupled with a correlated insulating substrate, electronic states that cannot be revealed in either individual layer may emerge in a synergistic manner. Here, we theoretically study the correlated and topological states in Coulomb-coupled and gate-tunable graphene-insulator heterostructures. By electrostatically aligning the electronic bands, charge carriers transferred between graphene and the insulator can yield a long-wavelength electronic crystal at the interface, exerting a superlattice Coulomb potential on graphene and generating topologically nontrivial subbands. This coupling can further boost electron-electron interaction effects in graphene, leading to a spontaneous bandgap formation at the Dirac point and interaction-enhanced Fermi velocity. Reciprocally, the electronic crystal at the interface is substantially stabilized with the help of cooperative interlayer Coulomb coupling. We propose a number of substrate candidates for graphene to experimentally demonstrate these effects.
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Affiliation(s)
- Xin Lu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - Shihao Zhang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - Yaning Wang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
| | - Xiang Gao
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, 030006, Taiyuan, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, 030006, Taiyuan, China
| | - Kaining Yang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, 030006, Taiyuan, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, 030006, Taiyuan, China
| | - Zhongqing Guo
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - Yuchen Gao
- Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China
- State Key Lab for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing, 100871, China
| | - Yu Ye
- Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China
- State Key Lab for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing, 100871, China
| | - Zheng Han
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, 030006, Taiyuan, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, 030006, Taiyuan, China
| | - Jianpeng Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, 201210, China.
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai, 201210, China.
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8
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Lyu P, Sødequist J, Sheng X, Qiu Z, Tadich A, Li Q, Edmonds MT, Zhao M, Redondo J, Švec M, Song P, Olsen T, Lu J. Gate-Tunable Renormalization of Spin-Correlated Flat-Band States and Bandgap in a 2D Magnetic Insulator. ACS NANO 2023; 17:15441-15448. [PMID: 37552585 DOI: 10.1021/acsnano.3c01038] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
Emergent quantum phenomena in two-dimensional van der Waal (vdW) magnets are largely governed by the interplay between exchange and Coulomb interactions. The ability to precisely tune the Coulomb interaction enables the control of spin-correlated flat-band states, band gap, and unconventional magnetism in such strongly correlated materials. Here, we demonstrate a gate-tunable renormalization of spin-correlated flat-band states and bandgap in magnetic chromium tribromide (CrBr3) monolayers grown on graphene. Our gate-dependent scanning tunneling spectroscopy (STS) studies reveal that the interflat-band spacing and bandgap of CrBr3 can be continuously tuned by 120 and 240 meV, respectively, via electrostatic injection of carriers into the hybrid CrBr3/graphene system. This can be attributed to the self-screening of CrBr3 arising from the gate-induced carriers injected into CrBr3, which dominates over the weakened remote screening of the graphene substrate due to the decreased carrier density in graphene. Precise tuning of the spin-correlated flat-band states and bandgap in 2D magnets via electrostatic modulation of Coulomb interactions not only provides effective strategies for optimizing the spin transport channels but also may exert a crucial influence on the exchange energy and spin-wave gap, which could raise the critical temperature for magnetic order.
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Affiliation(s)
- Pin Lyu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117544, Singapore
| | - Joachim Sødequist
- Department of Physics, Computational Atomic-Scale Materials Design (CAMD), Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Xiaoyu Sheng
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Zhizhan Qiu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117544, Singapore
| | - Anton Tadich
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria 3800, Australia
- Australian Synchrotron, Clayton, Victoria 3168, Australia
| | - Qile Li
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria 3800, Australia
- School of Physics and Astronomy, Monash University, Clayton, Victoria 3800, Australia
| | - Mark T Edmonds
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, Victoria 3800, Australia
- School of Physics and Astronomy, Monash University, Clayton, Victoria 3800, Australia
| | - Meng Zhao
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Jesús Redondo
- Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10, 162 00 Prague 6, Czech Republic
- Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague, Czech Republic
| | - Martin Švec
- Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague, Czech Republic
| | - Peng Song
- School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798,Singapore
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798,Singapore
| | - Thomas Olsen
- Department of Physics, Computational Atomic-Scale Materials Design (CAMD), Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Jiong Lu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117544, Singapore
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9
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Yang K, Gao X, Wang Y, Zhang T, Gao Y, Lu X, Zhang S, Liu J, Gu P, Luo Z, Zheng R, Cao S, Wang H, Sun X, Watanabe K, Taniguchi T, Li X, Zhang J, Dai X, Chen JH, Ye Y, Han Z. Unconventional correlated insulator in CrOCl-interfaced Bernal bilayer graphene. Nat Commun 2023; 14:2136. [PMID: 37059725 PMCID: PMC10104821 DOI: 10.1038/s41467-023-37769-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 03/30/2023] [Indexed: 04/16/2023] Open
Abstract
The realization of graphene gapped states with large on/off ratios over wide doping ranges remains challenging. Here, we investigate heterostructures based on Bernal-stacked bilayer graphene (BLG) atop few-layered CrOCl, exhibiting an over-1-GΩ-resistance insulating state in a widely accessible gate voltage range. The insulating state could be switched into a metallic state with an on/off ratio up to 107 by applying an in-plane electric field, heating, or gating. We tentatively associate the observed behavior to the formation of a surface state in CrOCl under vertical electric fields, promoting electron-electron (e-e) interactions in BLG via long-range Coulomb coupling. Consequently, at the charge neutrality point, a crossover from single particle insulating behavior to an unconventional correlated insulator is enabled, below an onset temperature. We demonstrate the application of the insulating state for the realization of a logic inverter operating at low temperatures. Our findings pave the way for future engineering of quantum electronic states based on interfacial charge coupling.
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Affiliation(s)
- Kaining Yang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, PR China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, PR China
| | - Xiang Gao
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, PR China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, PR China
| | - Yaning Wang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
- School of Material Science and Engineering, University of Science and Technology of China, Anhui, China
| | - Tongyao Zhang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, PR China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, PR China
| | - Yuchen Gao
- Collaborative Innovation Center of Quantum Matter, Beijing, China
- State Key Lab for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing, China
| | - Xin Lu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China.
| | - Shihao Zhang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China
| | - Jianpeng Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai, China
| | - Pingfan Gu
- Collaborative Innovation Center of Quantum Matter, Beijing, China
- State Key Lab for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing, China
| | - Zhaoping Luo
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
| | - Runjie Zheng
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
| | - Shimin Cao
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
- Beijing Academy of Quantum Information Sciences, Beijing, China
| | - Hanwen Wang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
| | - Xingdan Sun
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
| | - 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
| | - Xiuyan Li
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
| | - Jing Zhang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, PR China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, PR China
| | - Xi Dai
- Materials Department, University of California, Santa Barbara, CA, USA.
- Department of Physics, The Hongkong University of Science and Technology, Hong Kong, China.
| | - Jian-Hao Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China.
- Beijing Academy of Quantum Information Sciences, Beijing, China.
- Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing, China.
- Hefei National Laboratory, Hefei, China.
| | - Yu Ye
- Collaborative Innovation Center of Quantum Matter, Beijing, China.
- State Key Lab for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing, China.
| | - Zheng Han
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, PR China.
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, PR China.
- Liaoning Academy of Materials, Shenyang, China.
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10
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Wang Y, Gao X, Yang K, Gu P, Lu X, Zhang S, Gao Y, Ren N, Dong B, Jiang Y, Watanabe K, Taniguchi T, Kang J, Lou W, Mao J, Liu J, Ye Y, Han Z, Chang K, Zhang J, Zhang Z. Quantum Hall phase in graphene engineered by interfacial charge coupling. NATURE NANOTECHNOLOGY 2022; 17:1272-1279. [PMID: 36411376 PMCID: PMC9747608 DOI: 10.1038/s41565-022-01248-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 09/29/2022] [Indexed: 06/05/2023]
Abstract
The quantum Hall effect can be substantially affected by interfacial coupling between the host two-dimensional electron gases and the substrate, and has been predicted to give rise to exotic topological states. Yet the understanding of the underlying physics and the controllable engineering of this interaction remains challenging. Here we demonstrate the observation of an unusual quantum Hall effect, which differs markedly from that of the known picture, in graphene samples in contact with an antiferromagnetic insulator CrOCl equipped with dual gates. Two distinct quantum Hall phases are developed, with the Landau levels in monolayer graphene remaining intact at the conventional phase, but largely distorted for the interfacial-coupling phase. The latter quantum Hall phase is even present close to the absence of a magnetic field, with the consequential Landau quantization following a parabolic relation between the displacement field and the magnetic field. This characteristic prevails up to 100 K in a wide effective doping range from 0 to 1013 cm-2.
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Affiliation(s)
- Yaning Wang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, P. R. China
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, P. R. China
- School of Material Science and Engineering, University of Science and Technology of China, Shenyang, China
- Liaoning Academy of Materials, Shenyang, China
| | - Xiang Gao
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, P. R. China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, P. R. China
| | - Kaining Yang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, P. R. China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, P. R. China
| | - Pingfan Gu
- Collaborative Innovation Center of Quantum Matter, Beijing, China
- State Key Lab for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing, China
| | - Xin Lu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China
| | - Shihao Zhang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai, China
| | - Yuchen Gao
- Collaborative Innovation Center of Quantum Matter, Beijing, China
- State Key Lab for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing, China
| | - Naijie Ren
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, P. R. China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, P. R. China
| | - Baojuan Dong
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, P. R. China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, P. R. China
| | - Yuhang Jiang
- College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing, China
| | - 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
| | - Jun Kang
- Beijing Computational Science Research Center, Beijing, China
| | - Wenkai Lou
- State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China
| | - Jinhai Mao
- School of Physical Sciences and CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, China.
| | - Jianpeng Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China.
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai, China.
| | - Yu Ye
- Collaborative Innovation Center of Quantum Matter, Beijing, China.
- State Key Lab for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing, China.
| | - Zheng Han
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, P. R. China.
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, P. R. China.
- Liaoning Academy of Materials, Shenyang, China.
| | - Kai Chang
- State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China.
| | - Jing Zhang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan, P. R. China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, P. R. China
| | - Zhidong Zhang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
- School of Material Science and Engineering, University of Science and Technology of China, Shenyang, China
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