1
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Shilov AL, Kashchenko MA, Pantaleón Peralta PA, Wang Y, Kravtsov M, Kudriashov A, Zhan Z, Taniguchi T, Watanabe K, Slizovskiy S, Novoselov KS, Fal'ko VI, Guinea F, Bandurin DA. High-Mobility Compensated Semimetals, Orbital Magnetization, and Umklapp Scattering in Bilayer Graphene Moiré Superlattices. ACS Nano 2024. [PMID: 38648369 DOI: 10.1021/acsnano.3c13212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
Twist-controlled moiré superlattices (MSs) have emerged as a versatile platform for realizing artificial systems with complex electronic spectra. The combination of Bernal-stacked bilayer graphene (BLG) and hexagonal boron nitride (hBN) can give rise to an interesting MS, which has recently featured a set of unexpected behaviors, such as unconventional ferroelectricity and the electronic ratchet effect. Yet, the understanding of the electronic properties of BLG/hBN MS has, at present, remained fairly limited. Here, we combine magneto-transport and low-energy sub-THz excitation to gain insights into the properties of this MS. We demonstrate that the alignment between BLG and hBN crystal lattices results in the emergence of compensated semimetals at some integer fillings of the moiré bands, separated by van Hove singularities where the Lifshitz transition occurs. A particularly pronounced semimetal develops when eight holes reside in the moiré unit cell, where coexisting high-mobility electron and hole systems feature strong magnetoresistance reaching 2350% already at B = 0.25 T. Next, by measuring the THz-driven Nernst effect in remote bands, we observe valley splitting, indicating an orbital magnetization characterized by a strongly enhanced effective gv-factor of 340. Finally, using THz photoresistance measurements, we show that the high-temperature conductivity of the BLG/hBN MS is limited by electron-electron umklapp processes. Our multifaceted analysis introduces THz-driven magnetotransport as a convenient tool to probe the band structure and interaction effects in van der Waals materials and provides a comprehensive understanding of the BLG/hBN MS.
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Affiliation(s)
- Artur L Shilov
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
| | - Mikhail A Kashchenko
- Programmable Functional Materials Lab, Center for Neurophysics and Neuromorphic Technologies, Moscow 127495, Russia
| | | | - Yibo Wang
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117575, Singapore
| | - Mikhail Kravtsov
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117575, Singapore
| | - Andrei Kudriashov
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117575, Singapore
| | - Zhen Zhan
- IMDEA Nanoscience, Faraday 9, Madrid 28015, Spain
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute of Material Science, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute of Material Science, Tsukuba 305-0044, Japan
| | - Sergey Slizovskiy
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, U.K
| | - Kostya S Novoselov
- Institute for Functional Intelligent Materials, National University of Singapore, Singapore 117575, Singapore
| | - Vladimir I Fal'ko
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, U.K
| | - Francisco Guinea
- IMDEA Nanoscience, Faraday 9, Madrid 28015, Spain
- Donostia International Physics Center, Paseo Manuel de Lardizábal 4, San Sebastián 20018, Spain
| | - Denis A Bandurin
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
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2
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Wu K, Wang H, Yang M, Liu L, Sun Z, Hu G, Song Y, Han X, Guo J, Wu K, Feng B, Shen C, Huang Y, Shi Y, Cheng Z, Yang H, Bao L, Pantelides ST, Gao HJ. Gold-Template-Assisted Mechanical Exfoliation of Large-Area 2D Layers Enables Efficient and Precise Construction of Moiré Superlattices. Adv Mater 2024:e2313511. [PMID: 38597395 DOI: 10.1002/adma.202313511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 04/07/2024] [Indexed: 04/11/2024]
Abstract
Moiré superlattices, consisting of rotationally aligned 2D atomically thin layers, provide a highly novel platform for the study of correlated quantum phenomena. However, reliable and efficient construction of moiré superlattices is challenging because of difficulties to accurately angle-align small exfoliated 2D layers and the need to shun wet-transfer processes. Here, efficient and precise construction of various moiré superlattices is demonstrated by picking up and stacking large-area 2D mono- or few-layer crystals with predetermined crystal axes, made possible by a gold-template-assisted mechanical exfoliation method. The exfoliated 2D layers are semiconductors, superconductors, or magnets and their high quality is confirmed by photoluminescence and Raman spectra and by electrical transport measurements of fabricated field-effect transistors and Hall devices. Twisted homobilayers with angle-twisting accuracy of ≈0.3°, twisted heterobilayers with sub-degree angle-alignment accuracy, and multilayer superlattices are precisely constructed and characterized by their moiré patterns, interlayer excitons, and second harmonic generation. The present study paves the way for exploring emergent phenomena in moiré superlattices.
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Affiliation(s)
- Kang Wu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Hao Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Meng Yang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Li Liu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Zhenyu Sun
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Guojing Hu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Yanpeng Song
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Xin Han
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing, 100049, P. R. China
| | - Jiangang Guo
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Kehui Wu
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Baojie Feng
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Chengmin Shen
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Yuan Huang
- Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing, 100081, P. R. China
| | - Youguo Shi
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing, 100049, P. R. China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, P. R. China
| | - Zhigang Cheng
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, P. R. China
| | - Haitao Yang
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Hefei National Laboratory, Hefei, Anhui, 230088, P. R. China
| | - Lihong Bao
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Hefei National Laboratory, Hefei, Anhui, 230088, P. R. China
| | - Sokrates T Pantelides
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Department of Physics and Astronomy & Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, 37235, USA
| | - Hong-Jun Gao
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Hefei National Laboratory, Hefei, Anhui, 230088, P. R. China
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3
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Cai CS, Lai WY, Liu PH, Chou TC, Liu RY, Lin CM, Gwo S, Hsu WT. Ultralow Auger-Assisted Interlayer Exciton Annihilation in WS 2/WSe 2 Moiré Heterobilayers. Nano Lett 2024; 24:2773-2781. [PMID: 38285707 PMCID: PMC10921466 DOI: 10.1021/acs.nanolett.3c04688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 01/22/2024] [Accepted: 01/23/2024] [Indexed: 01/31/2024]
Abstract
Transition metal dichalcogenide (TMD) heterobilayers have emerged as a promising platform for exploring solid-state quantum simulators and many-body quantum phenomena. Their type II band alignment, combined with the moiré superlattice, inevitably leads to nontrivial exciton interactions and dynamics. Here, we unveil the distinct Auger annihilation processes for delocalized interlayer excitons in WS2/WSe2 moiré heterobilayers. By fitting the characteristic efficiency droop and bimolecular recombination rate, we quantitatively determine an ultralow Auger coefficient of 1.3 × 10-5 cm2 s-1, which is >100-fold smaller than that of excitons in TMD monolayers. In addition, we reveal selective exciton upconversion into the WSe2 layer, which highlights the significance of intralayer electron Coulomb interactions in dictating the microscopic scattering pathways. The distinct Auger processes arising from spatial electron-hole separation have important implications for TMD heterobilayers while endowing interlayer excitons and their strongly correlated states with unique layer degrees of freedom.
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Affiliation(s)
- Cheng-Syuan Cai
- Department
of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- National
Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Wei-Yan Lai
- Department
of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Po-Hsuan Liu
- Department
of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Tzu-Chieh Chou
- Department
of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- National
Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Ro-Ya Liu
- National
Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Chih-Ming Lin
- Department
of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Shangjr Gwo
- Department
of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Wei-Ting Hsu
- Department
of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- National
Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
- Research
Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
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4
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Pendharkar M, Tran SJ, Zaborski G, Finney J, Sharpe AL, Kamat RV, Kalantre SS, Hocking M, Bittner NJ, Watanabe K, Taniguchi T, Pittenger B, Newcomb CJ, Kastner MA, Mannix AJ, Goldhaber-Gordon D. Torsional force microscopy of van der Waals moirés and atomic lattices. Proc Natl Acad Sci U S A 2024; 121:e2314083121. [PMID: 38427599 DOI: 10.1073/pnas.2314083121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 01/11/2024] [Indexed: 03/03/2024] Open
Abstract
In a stack of atomically thin van der Waals layers, introducing interlayer twist creates a moiré superlattice whose period is a function of twist angle. Changes in that twist angle of even hundredths of a degree can dramatically transform the system's electronic properties. Setting a precise and uniform twist angle for a stack remains difficult; hence, determining that twist angle and mapping its spatial variation is very important. Techniques have emerged to do this by imaging the moiré, but most of these require sophisticated infrastructure, time-consuming sample preparation beyond stack synthesis, or both. In this work, we show that torsional force microscopy (TFM), a scanning probe technique sensitive to dynamic friction, can reveal surface and shallow subsurface structure of van der Waals stacks on multiple length scales: the moirés formed between bi-layers of graphene and between graphene and hexagonal boron nitride (hBN) and also the atomic crystal lattices of graphene and hBN. In TFM, torsional motion of an Atomic Force Microscope (AFM) cantilever is monitored as it is actively driven at a torsional resonance while a feedback loop maintains contact at a set force with the sample surface. TFM works at room temperature in air, with no need for an electrical bias between the tip and the sample, making it applicable to a wide array of samples. It should enable determination of precise structural information including twist angles and strain in moiré superlattices and crystallographic orientation of van der Waals flakes to support predictable moiré heterostructure fabrication.
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Affiliation(s)
- Mihir Pendharkar
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305
| | - Steven J Tran
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Physics, Stanford University, Stanford, CA 94305
| | - Gregory Zaborski
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305
| | - Joe Finney
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Physics, Stanford University, Stanford, CA 94305
| | - Aaron L Sharpe
- Materials Physics Department, Sandia National Laboratories, Livermore, CA 94550
| | - Rupini V Kamat
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Physics, Stanford University, Stanford, CA 94305
| | - Sandesh S Kalantre
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Physics, Stanford University, Stanford, CA 94305
| | - Marisa Hocking
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305
| | | | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
| | | | | | - Marc A Kastner
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Physics, Stanford University, Stanford, CA 94305
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Andrew J Mannix
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305
| | - David Goldhaber-Gordon
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
- Department of Physics, Stanford University, Stanford, CA 94305
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5
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Liu H, Wang J, Chen S, Sun Z, Xu H, Han Y, Wang C, Liu H, Huang L, Luo J, Liu D. Direct Visualization of Dark Interlayer Exciton Transport in Moiré Superlattices. Nano Lett 2024; 24:339-346. [PMID: 38147355 DOI: 10.1021/acs.nanolett.3c04105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Moiré superlattices have emerged as an unprecedented manipulation tool for engineering correlated quantum phenomena in van der Waals heterostructures. With moiré potentials as a naturally configurable solid-state that sustains high exciton density, interlayer excitons in transition metal dichalcogenide heterostructures are expected to achieve high-temperature exciton condensation. However, the exciton degeneracy state is usually optically inactive due to the finite momentum of interlayer excitons. Experimental observation of dark interlayer excitons in moiré potentials remains challenging. Here we directly visualize the dark interlayer exciton transport in WS2/h-BN/WSe2 heterostructures using femtosecond transient absorption microscopy. We observe a transition from classical free exciton gas to quantum degeneracy by imaging temperature-dependent exciton transport. Below a critical degeneracy temperature, exciton diffusion rates exhibit an accelerating downward trend, which can be explained well by a nonlinear quantum diffusion model. These results open the door to quantum information processing and high-precision metrology in moiré superlattices.
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Affiliation(s)
- Huan Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Jiangcai Wang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Shihong Chen
- School of Resources, Environment and Materials, Guangxi University, Nanning 530004, China
| | - Zejun Sun
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Haowen Xu
- Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China
| | - Yishu Han
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Chong Wang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Huixian Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Li Huang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Jianbin Luo
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Dameng Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
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6
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Qian W, Qi P, Dai Y, Shi B, Tao G, Liu H, Zhang X, Xiang D, Fang Z, Liu W. Strongly Localized Moiré Exciton in Twisted Homobilayers. Small 2024; 20:e2305200. [PMID: 37649150 DOI: 10.1002/smll.202305200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 07/14/2023] [Indexed: 09/01/2023]
Abstract
Artificially molding exciton flux is the cornerstone for developing promising excitonic devices. In the emerging hetero/homobilayers, the spatial separated charges prolong exciton lifetimes and create out-plane dipoles, facilitating electrically control exciton flux on a large scale, and the nanoscale periodic moiré potentials arising from twist-angle or/and lattice mismatch can substantially alter exciton dynamics, which are mainly proved in the heterostructures. However, the spatially indirect excitons dynamics in homobilayers without lattice mismatch remain elusive. Here the nonequilibrium dynamics of indirect exciton in homobilayers are systematically investigated. The homobilayers with slightly twist-angle can induce a deep moiré potential (>50 meV) in the energy landscape of indirect excitons, resulting in a strongly localized moiré excitons insulating the transport dynamics from phonons and disorder. These findings provide insights into the exciton dynamics and many-body physics in moiré superlattices modulated energy landscape, with implications for designing excitonic devices operating at room temperature.
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Affiliation(s)
- Wenqi Qian
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Pengfei Qi
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Yuchen Dai
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing, 100871, China
| | - Beibei Shi
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing, 100871, China
| | - Guangyi Tao
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing, 100871, China
| | - Haiyi Liu
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Xubin Zhang
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Dong Xiang
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Zheyu Fang
- School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, Beijing, 100871, China
| | - Weiwei Liu
- Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
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7
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Sari B, Zeltmann SE, Zhao C, Pelz PM, Javey A, Minor AM, Ophus C, Scott MC. Analysis of Strain and Defects in Tellurium-WSe 2 Moiré Heterostructures Using Scanning Nanodiffraction. ACS Nano 2023; 17:22326-22333. [PMID: 37956410 PMCID: PMC10690779 DOI: 10.1021/acsnano.3c04283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Revised: 11/02/2023] [Accepted: 11/03/2023] [Indexed: 11/15/2023]
Abstract
In recent years, there has been an increasing focus on 2D nongraphene materials that range from insulators to semiconductors to metals. As a single-elemental van der Waals semiconductor, tellurium (Te) has captivating anisotropic physical properties. Recent work demonstrated growth of ultrathin Te on WSe2 with the atomic chains of Te aligned with the armchair directions of the substrate using physical vapor deposition (PVD). In this system, a moiré superlattice is formed where micrometer-scale Te flakes sit on top of the continuous WSe2 film. Here, we determined the precise orientation of the Te flakes with respect to the substrate and detailed structure of the resulting moiré lattice by combining electron microscopy with image simulations. We directly visualized the moiré lattice using center of mass-differential phase contrast (CoM-DPC). We also investigated the local strain within the Te/WSe2 layered materials using scanning nanodiffraction techniques. There is a significant tensile strain at the edges of flakes along the direction perpendicular to the Te chain direction, which is an indication of the preferred orientation for the growth of Te on WSe2. In addition, we observed local strain relaxation regions within the Te film, specifically attributed to misfit dislocations, which we characterize as having a screw-like nature. The detailed structural analysis gives insight into the growth mechanisms and strain relaxation in this moiré heterostructure.
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Affiliation(s)
- Bengisu Sari
- Department
of Materials Science and Engineering, University
of California Berkeley, Berkeley, California 94720, United States
- The
National Center for Electron Microscopy, Molecular Foundry, Berkeley, California 94720, United States
- Materials
Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720-8099, United States
| | - Steven E. Zeltmann
- Department
of Materials Science and Engineering, University
of California Berkeley, Berkeley, California 94720, United States
| | - Chunsong Zhao
- Department
of Materials Science and Engineering, University
of California Berkeley, Berkeley, California 94720, United States
- Materials
Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720-8099, United States
- Department
of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California 94720, United States
| | - Philipp M. Pelz
- Institute
of Micro- and Nanostructure Research, Center for Nanoanalysis and
Electron Microscopy, Interdisciplinary Center for Nanostructured Films, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen 91058, Germany
| | - Ali Javey
- Materials
Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720-8099, United States
- Department
of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California 94720, United States
| | - Andrew M. Minor
- Department
of Materials Science and Engineering, University
of California Berkeley, Berkeley, California 94720, United States
- The
National Center for Electron Microscopy, Molecular Foundry, Berkeley, California 94720, United States
| | - Colin Ophus
- The
National Center for Electron Microscopy, Molecular Foundry, Berkeley, California 94720, United States
| | - Mary C. Scott
- Department
of Materials Science and Engineering, University
of California Berkeley, Berkeley, California 94720, United States
- The
National Center for Electron Microscopy, Molecular Foundry, Berkeley, California 94720, United States
- Materials
Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720-8099, United States
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8
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Wen Y, Coupin MJ, Hou L, Warner JH. Moiré Superlattice Structure of Pleated Trilayer Graphene Imaged by 4D Scanning Transmission Electron Microscopy. ACS Nano 2023; 17:19600-19612. [PMID: 37791789 DOI: 10.1021/acsnano.2c12179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Moiré superlattices in graphene arise from rotational twists in stacked 2D layers, leading to specific band structures, charge density and interlayer electron and excitonic interactions. The periodicities in bilayer graphene moiré lattices are given by a simple moiré basis vector that describes periodic oscillations in atomic density. The addition of a third layer to form trilayer graphene generates a moiré lattice comprised of multiple harmonics that do not occur in bilayer systems, leading to nontrivial crystal symmetries. Here, we use atomic resolution 4D-scanning transmission electron microscopy to study atomic structure in bilayer and trilayer graphene moiré superlattices and use 4D-STEM to map the electric fields to show subtle variations in the long-range moiré patterns. We show that monolayer graphene folded into an S-bend graphene pleat produces trilayer moiré superlattices with both small (<2°) and larger twist angles (7-30°). Annular in-plane electric field concentrations are detected in high angle bilayers due to overlapping rotated graphene hexagons in each layer. The presence of a third low angle twisted layer in S-bend trilayer graphene, introduces a long-range modulation of the atomic structure so that no real space unit cell is detected. By directly imaging trilayer moiré harmonics that span from picoscale to nanoscale using 4D-STEM, we gain insights into the complex spatial distributions of atomic density and electric fields in trilayer twisted layered materials.
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Affiliation(s)
- Yi Wen
- Department of Materials, University of Oxford, Oxford OX1 3PH, United Kingdom
| | - Matthew J Coupin
- Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Linlin Hou
- Department of Materials, University of Oxford, Oxford OX1 3PH, United Kingdom
| | - Jamie H Warner
- Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States
- Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
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9
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Liu M, Senga R, Koshino M, Lin YC, Suenaga K. Direct Observation of Locally Modified Excitonic Effects within a Moiré Unit Cell in Twisted Bilayer Graphene. ACS Nano 2023; 17:18433-18440. [PMID: 37682623 DOI: 10.1021/acsnano.3c06021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/10/2023]
Abstract
Bilayer graphene, which forms moiré superlattices, possesses distinct electronic and optical properties owing to its hybridized energy band and the emergence of van Hove singularities depending on its twist angle. Extensive research has been conducted on the global characteristics of moiré superlattices induced by their long-range periodicity. However, the local properties, which differ owing to the variations in the three-dimensional atomic arrangement, within a moiré unit cell have been rarely explored. In this study, we demonstrate the highly localized excitation of carbon 1s electrons to unoccupied van Hove singularities in twisted bilayer graphene by electron energy loss spectroscopy using a monochromated transmission electron microscope. The core-level excitations associated with the van Hove singularities exhibit a systematic twist-angle dependence analogous to optical excitations. Furthermore, local variations in the core-level van Hove singularity peaks, which can originate from the core-exciton lifetimes and band modifications corresponding to the local stacking geometry within a moiré unit cell, are unambiguously corroborated.
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Affiliation(s)
- Ming Liu
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
| | - Ryosuke Senga
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1-1, Tsukuba 305-8565, Japan
| | - Masanori Koshino
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1-1, Tsukuba 305-8565, Japan
| | - Yung-Chang Lin
- Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1-1, Tsukuba 305-8565, Japan
| | - Kazu Suenaga
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
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10
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Zheng H, Guo H, Chen S, Wu B, Li S, He J, Liu Z, Lu G, Duan X, Pan A, Liu Y. Strong Interlayer Coupling in Twisted Transition Metal Dichalcogenide Moiré Superlattices. Adv Mater 2023; 35:e2210909. [PMID: 36708237 DOI: 10.1002/adma.202210909] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 01/12/2023] [Indexed: 06/18/2023]
Abstract
Moiré superlattices in twisted van der Waals materials offer a powerful platform for exploring light-matter interactions. The periodic moiré potentials in moiré superlattices can induce strongly correlated quantum phenomena that depend on the moiré potential associated with interlayer coupling at the interface. However, moiré superlattices are primarily prepared by mechanical exfoliation and manual stacking, where the transfer methods easily cause interfacial contamination, and the preparation of high-quality bilayer 2D materials with small twist angles by growth methods remains a significant challenge. In this work, WSe2 /WSe2 homobilayers with different twist angles by chemical vapor deposition (CVD), using a heteroatom-assisted growth technique, are synthesized. Using low-frequency Raman scattering, the uniformity of the moiré superlattices is mapped to demonstrate the strong interfacial coupling of the CVD-fabricated twist-angle homobilayers. The moiré potential depths of the CVD-grown and artificially stacked homostructures with twist angles of 1.5° are 115 and 45 meV (an increase of 155%), indicating that the depth of moiré potential can be modulated by the interfacial coupling. These results open a new avenue to study the modulation of moiré potential by strong interlayer coupling and provide a foundation for the development of twistronics.
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Affiliation(s)
- Haihong Zheng
- School of Physics and Electronics, Hunan Key Laboratory for Super-microstructure and Ultrafast Process, Central South University, 932 South Lushan Road, Changsha, Hunan, 410083, P. R. China
| | - Hongli Guo
- Department of Physics and Astronomy, California State University Northridge, California, CA, 91330-8268, USA
| | - Shula Chen
- Hunan Institute of Optoelectronic Integration, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Biao Wu
- School of Physics and Electronics, Hunan Key Laboratory for Super-microstructure and Ultrafast Process, Central South University, 932 South Lushan Road, Changsha, Hunan, 410083, P. R. China
| | - Shaofei Li
- School of Physics and Electronics, Hunan Key Laboratory for Super-microstructure and Ultrafast Process, Central South University, 932 South Lushan Road, Changsha, Hunan, 410083, P. R. China
| | - Jun He
- School of Physics and Electronics, Hunan Key Laboratory for Super-microstructure and Ultrafast Process, Central South University, 932 South Lushan Road, Changsha, Hunan, 410083, P. R. China
| | - Zongwen Liu
- School of Chemical and Biomolecular Engineering, The University of Sydney, Camperdown, NSW, 2006, Australia
- The University of Sydney Nano Institute, The University of Sydney, Camperdown, NSW, 2006, Australia
| | - Gang Lu
- Department of Physics and Astronomy, California State University Northridge, California, CA, 91330-8268, USA
| | - Xidong Duan
- Hunan Key Laboratory of 2D Materials and State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, P. R. China
| | - Anlian Pan
- Hunan Institute of Optoelectronic Integration, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - 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, P. R. China
- State Key Laboratory of High-Performance Complex Manufacturing, Central South University, 932 South Lushan Road, Changsha, Hunan, 410083, P. R. China
- Shenzhen Research Institute of Central South University, Shenzhen, 51800, P. R. China
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11
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Zheng H, Wu B, Wang CT, Li S, He J, Liu Z, Wang JT, Duan JA, Liu Y. Moiré Enhanced Potentials in Twisted Transition Metal Dichalcogenide Trilayers Homostructures. Small 2023:e2207988. [PMID: 36938893 DOI: 10.1002/smll.202207988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 03/03/2023] [Indexed: 06/18/2023]
Abstract
The exploration of moiré superlatticesholds promising potential to uncover novel quantum phenomena emerging from the interplay of atomic structure and electronic correlation . However, the impact of the moiré potential modulation on the number of twisted layers has yet to be experimentally explored. Here, this work synthesizes a twisted WSe2 homotrilayer using a dry-transfer method and investigates the enhancement of the moiré potential with increasing number of twisted layers. The results of the study reveal the presence of multiple exciton resonances with positive or negative circularly polarized emission in the WSe2 homostructure with small twist angles, which are attributed to the excitonic ground and excited states confined to the moiré potential. The distinct g-factor observed in the magneto-optical spectroscopy is also shown to be a result of the confinement of the exciton in the moiré potential. The moiré potential depths of the twisted bilayer and trilayer homostructures are found to be 111 and 212 meV, respectively, an increase of 91% from the bilayer structure. These findings demonstrate that the depth of the moiré potential can be manipulated by adjusting the number of stacked layers, providing a promising avenue for exploration into highly correlated quantum phenomena.
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Affiliation(s)
- Haihong Zheng
- 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
- State Key Laboratory of High-Performance Complex Manufacturing, Central South University, 932 South Lushan Road, Changsha, Hunan, 410083, People's Republic of China
| | - Biao Wu
- 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
- State Key Laboratory of High-Performance Complex Manufacturing, Central South University, 932 South Lushan Road, Changsha, Hunan, 410083, People's Republic of China
| | - Chang-Tian Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Shaofei Li
- 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
| | - Jun He
- 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
| | - Zongwen Liu
- School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, NSW, 2006, Australia
- The University of Sydney Nano Institute, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Jian-Tao Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, People's Republic of China
| | - Ji-An Duan
- State Key Laboratory of High-Performance Complex Manufacturing, Central South University, 932 South Lushan Road, Changsha, Hunan, 410083, People's Republic of China
| | - 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
- State Key Laboratory of High-Performance Complex Manufacturing, Central South University, 932 South Lushan Road, Changsha, Hunan, 410083, People's Republic of China
- Shenzhen Research Institute of Central South University, Shenzhen, 518057, People's Republic of China
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12
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Lyu B, Chen J, Lou S, Li C, Qiu L, Ouyang W, Xie J, Mitchell I, Wu T, Deng A, Hu C, Zhou X, Shen P, Ma S, Wu Z, Watanabe K, Taniguchi T, Wang X, Liang Q, Jia J, Urbakh M, Hod O, Ding F, Wang S, Shi Z. Catalytic Growth of Ultralong Graphene Nanoribbons on Insulating Substrates. Adv Mater 2022; 34:e2200956. [PMID: 35560711 DOI: 10.1002/adma.202200956] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 04/18/2022] [Indexed: 06/15/2023]
Abstract
Graphene nanoribbons (GNRs) with widths of a few nanometers are promising candidates for future nanoelectronic applications due to their structurally tunable bandgaps, ultrahigh carrier mobilities, and exceptional stability. However, the direct growth of micrometer-long GNRs on insulating substrates, which is essential for the fabrication of nanoelectronic devices, remains an immense challenge. Here, the epitaxial growth of GNRs on an insulating hexagonal boron nitride (h-BN) substrate through nanoparticle-catalyzed chemical vapor deposition is reported. Ultranarrow GNRs with lengths of up to 10 µm are synthesized. Remarkably, the as-grown GNRs are crystallographically aligned with the h-BN substrate, forming 1D moiré superlattices. Scanning tunneling microscopy reveals an average width of 2 nm and a typical bandgap of ≈1 eV for similar GNRs grown on conducting graphite substrates. Fully atomistic computational simulations support the experimental results and reveal a competition between the formation of GNRs and carbon nanotubes during the nucleation stage, and van der Waals sliding of the GNRs on the h-BN substrate throughout the growth stage. This study provides a scalable, single-step method for growing micrometer-long narrow GNRs on insulating substrates, thus opening a route to explore the performance of high-quality GNR devices and the fundamental physics of 1D moiré superlattices.
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Affiliation(s)
- Bosai Lyu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Jiajun Chen
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Shuo Lou
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Can Li
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Lu Qiu
- Centre for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan, 44919, South Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, South Korea
| | - Wengen Ouyang
- Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan, Hubei, 430072, China
| | - Jingxu Xie
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Izaac Mitchell
- Centre for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan, 44919, South Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, South Korea
| | - Tongyao Wu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Aolin Deng
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Cheng Hu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Xianliang Zhou
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Peiyue Shen
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Saiqun Ma
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Zhenghan Wu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Kenji Watanabe
- Research Centre for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- International Centre for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Xiaoqun Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Qi Liang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Jinfeng Jia
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Michael Urbakh
- Department of Physical Chemistry, School of Chemistry and The Sackler Centre for Computational Molecular and Materials Science, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Oded Hod
- Department of Physical Chemistry, School of Chemistry and The Sackler Centre for Computational Molecular and Materials Science, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Feng Ding
- Centre for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan, 44919, South Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, South Korea
| | - Shiyong Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Zhiwen Shi
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 200240, China
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13
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Chiodini S, Kerfoot J, Venturi G, Mignuzzi S, Alexeev EM, Teixeira Rosa B, Tongay S, Taniguchi T, Watanabe K, Ferrari AC, Ambrosio A. Moiré Modulation of Van Der Waals Potential in Twisted Hexagonal Boron Nitride. ACS Nano 2022; 16:7589-7604. [PMID: 35486712 PMCID: PMC9134503 DOI: 10.1021/acsnano.1c11107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
When a twist angle is applied between two layered materials (LMs), the registry of the layers and the associated change in their functional properties are spatially modulated, and a moiré superlattice arises. Several works explored the optical, electric, and electromechanical moiré-dependent properties of such twisted LMs but, to the best of our knowledge, no direct visualization and quantification of van der Waals (vdW) interlayer interactions has been presented, so far. Here, we use tapping mode atomic force microscopy phase-imaging to probe the spatial modulation of the vdW potential in twisted hexagonal boron nitride. We find a moiré superlattice in the phase channel only when noncontact (long-range) forces are probed, revealing the modulation of the vdW potential at the sample surface, following AB and BA stacking domains. The creation of scalable electrostatic domains, modulating the vdW potential at the interface with the environment by means of layer twisting, could be used for local adhesion engineering and surface functionalization by affecting the deposition of molecules or nanoparticles.
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Affiliation(s)
- Stefano Chiodini
- Center
for Nano Science and Technology, Fondazione
Istituto Italiano di Tecnologia, Via G. Pascoli 70, Milan 20133, Italy
| | - James Kerfoot
- Cambridge
Graphene Centre, University of Cambridge, 9, JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Giacomo Venturi
- Center
for Nano Science and Technology, Fondazione
Istituto Italiano di Tecnologia, Via G. Pascoli 70, Milan 20133, Italy
- Physics
Department, Politecnico Milano, P.zza Leonardo Da Vinci 32, Milan 20133, Italy
| | - Sandro Mignuzzi
- Cambridge
Graphene Centre, University of Cambridge, 9, JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Evgeny M. Alexeev
- Cambridge
Graphene Centre, University of Cambridge, 9, JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Bárbara Teixeira Rosa
- Cambridge
Graphene Centre, University of Cambridge, 9, JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Sefaattin Tongay
- School
for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, 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
| | - Andrea C. Ferrari
- Cambridge
Graphene Centre, University of Cambridge, 9, JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Antonio Ambrosio
- Center
for Nano Science and Technology, Fondazione
Istituto Italiano di Tecnologia, Via G. Pascoli 70, Milan 20133, Italy
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14
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Wang P, Lee W, Corbett JP, Koll WH, Vu NM, Laleyan DA, Wen Q, Wu Y, Pandey A, Gim J, Wang D, Qiu DY, Hovden R, Kira M, Heron JT, Gupta JA, Kioupakis E, Mi Z. Scalable Synthesis of Monolayer Hexagonal Boron Nitride on Graphene with Giant Bandgap Renormalization. Adv Mater 2022; 34:e2201387. [PMID: 35355349 DOI: 10.1002/adma.202201387] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/20/2022] [Indexed: 06/14/2023]
Abstract
Monolayer hexagonal boron nitride (hBN) has been widely considered a fundamental building block for 2D heterostructures and devices. However, the controlled and scalable synthesis of hBN and its 2D heterostructures has remained a daunting challenge. Here, an hBN/graphene (hBN/G) interface-mediated growth process for the controlled synthesis of high-quality monolayer hBN is proposed and further demonstrated. It is discovered that the in-plane hBN/G interface can be precisely controlled, enabling the scalable epitaxy of unidirectional monolayer hBN on graphene, which exhibits a uniform moiré superlattice consistent with single-domain hBN, aligned to the underlying graphene lattice. Furthermore, it is identified that the deep-ultraviolet emission at 6.12 eV stems from the 1s-exciton state of monolayer hBN with a giant renormalized direct bandgap on graphene. This work provides a viable path for the controlled synthesis of ultraclean, wafer-scale, atomically ordered 2D quantum materials, as well as the fabrication of 2D quantum electronic and optoelectronic devices.
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Affiliation(s)
- Ping Wang
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Woncheol Lee
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Joseph P Corbett
- Department of Physics, Ohio State University, Columbus, OH, 43210, USA
- UES Inc., 4401 Dayton-Xenia Rd, Dayton, OH, 45432, USA
| | - William H Koll
- Department of Physics, Ohio State University, Columbus, OH, 43210, USA
| | - Nguyen M Vu
- Department of Material Science and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - David Arto Laleyan
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Qiannan Wen
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Yuanpeng Wu
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Ayush Pandey
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Jiseok Gim
- Department of Material Science and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Ding Wang
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Diana Y Qiu
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06516, USA
| | - Robert Hovden
- Department of Material Science and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Mackillo Kira
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109, USA
| | - John T Heron
- Department of Material Science and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Jay A Gupta
- Department of Physics, Ohio State University, Columbus, OH, 43210, USA
| | - Emmanouil Kioupakis
- Department of Material Science and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Zetian Mi
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109, USA
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15
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Bian M, Zhu L, Wang X, Choi J, Chopdekar RV, Wei S, Wu L, Huai C, Marga A, Yang Q, Li YC, Yao F, Yu T, Crooker SA, Cheng XM, Sabirianov RF, Zhang S, Lin J, Hou Y, Zeng H. Dative Epitaxy of Commensurate Monocrystalline Covalent van der Waals Moiré Supercrystal. Adv Mater 2022; 34:e2200117. [PMID: 35236008 DOI: 10.1002/adma.202200117] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 02/28/2022] [Indexed: 06/14/2023]
Abstract
Realizing van der Waals (vdW) epitaxy in the 1980s represents a breakthrough that circumvents the stringent lattice matching and processing compatibility requirements in conventional covalent heteroepitaxy. However, due to the weak vdW interactions, there is little control over film qualities by the substrate. Typically, discrete domains with a spread of misorientation angles are formed, limiting the applicability of vdW epitaxy. Here, the epitaxial growth of monocrystalline, covalent Cr5 Te8 2D crystals on monolayer vdW WSe2 by chemical vapor deposition is reported, driven by interfacial dative bond formation. The lattice of Cr5 Te8 , with a lateral dimension of a few tens of micrometers, is fully commensurate with that of WSe2 via 3 × 3 (Cr5 Te8 )/7 × 7 (WSe2 ) supercell matching, forming a single-crystalline moiré superlattice. This work establishes a conceptually distinct paradigm of thin-film epitaxy, termed "dative epitaxy", which takes full advantage of covalent epitaxy with chemical bonding for fixing the atomic registry and crystal orientation, while circumventing its stringent lattice matching and processing compatibility requirements; conversely, it ensures the full flexibility of vdW epitaxy, while avoiding its poor orientation control. Cr5 Te8 2D crystals grown by dative epitaxy exhibit square magnetic hysteresis, suggesting minimized interfacial defects that can serve as pinning sites.
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Affiliation(s)
- Mengying Bian
- Beijing Key Laboratory for Magnetoelectric Materials and Devices, Beijing Innovation Center for Engineering Science and Advanced Technology, School of Materials Science and Engineering, Peking University, Beijing, 100871, China
- Department of Physics, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA
| | - Liang Zhu
- Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Xiao Wang
- Physics Department, Bryn Mawr College, Bryn Mawr, PA, 19010, USA
| | - Junho Choi
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Rajesh V Chopdekar
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Sichen Wei
- Department of Materials Design and Innovation, University at Buffalo, The State University of New York, Buffalo, NY, 14260, USA
| | - Lishu Wu
- Division of Physics & Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Chang Huai
- Department of Physics, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA
| | - Austin Marga
- Department of Physics, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA
| | - Qishuo Yang
- Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Yuguang C Li
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY, 14260, USA
| | - Fei Yao
- Department of Materials Design and Innovation, University at Buffalo, The State University of New York, Buffalo, NY, 14260, USA
| | - Ting Yu
- Division of Physics & Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Scott A Crooker
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Xuemei M Cheng
- Physics Department, Bryn Mawr College, Bryn Mawr, PA, 19010, USA
| | - Renat F Sabirianov
- Department of Physics, University of Nebraska-Omaha, Omaha, NE, 68182, USA
| | - Shengbai Zhang
- Department of Physics, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Junhao Lin
- Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Yanglong Hou
- Beijing Key Laboratory for Magnetoelectric Materials and Devices, Beijing Innovation Center for Engineering Science and Advanced Technology, School of Materials Science and Engineering, Peking University, Beijing, 100871, China
| | - Hao Zeng
- Department of Physics, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA
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16
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Hamer M, Giampietri A, Kandyba V, Genuzio F, Menteş TO, Locatelli A, Gorbachev RV, Barinov A, Mucha-Kruczyński M. Moiré Superlattice Effects and Band Structure Evolution in Near-30-Degree Twisted Bilayer Graphene. ACS Nano 2022; 16:1954-1962. [PMID: 35073479 PMCID: PMC9007532 DOI: 10.1021/acsnano.1c06439] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 01/20/2022] [Indexed: 06/01/2023]
Abstract
In stacks of two-dimensional crystals, mismatch of their lattice constants and misalignment of crystallographic axes lead to formation of moiré patterns. We show that moiré superlattice effects persist in twisted bilayer graphene (tBLG) with large twists and short moiré periods. Using angle-resolved photoemission, we observe dramatic changes in valence band topology across large regions of the Brillouin zone, including the vicinity of the saddle point at M and across 3 eV from the Dirac points. In this energy range, we resolve several moiré minibands and detect signatures of secondary Dirac points in the reconstructed dispersions. For twists θ > 21.8°, the low-energy minigaps are not due to cone anticrossing as is the case at smaller twist angles but rather due to moiré scattering of electrons in one graphene layer on the potential of the other which generates intervalley coupling. Our work demonstrates the robustness of the mechanisms which enable engineering of electronic dispersions of stacks of two-dimensional crystals by tuning the interface twist angles. It also shows that large-angle tBLG hosts electronic minigaps and van Hove singularities of different origin which, given recent progress in extreme doping of graphene, could be explored experimentally.
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Affiliation(s)
- Matthew
J. Hamer
- Department
of Physics, University of Manchester, Oxford Road, Manchester M13 9PL, United
Kingdom
- National
Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, United Kingdom
| | | | | | | | | | | | - Roman V. Gorbachev
- Department
of Physics, 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, Oxford
Road, Manchester M13 9PL, United Kingdom
| | | | - Marcin Mucha-Kruczyński
- Department
of Physics, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
- Centre
for Nanoscience and Nanotechnology, University
of Bath, Claverton Down, Bath BA2
7AY, United Kingdom
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17
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Zhao S, Kitaura R, Moon P, Koshino M, Wang F. Interlayer Interactions in 1D Van der Waals Moiré Superlattices. Adv Sci (Weinh) 2022; 9:e2103460. [PMID: 34841726 PMCID: PMC8805582 DOI: 10.1002/advs.202103460] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 10/02/2021] [Indexed: 06/13/2023]
Abstract
Studying two-dimensional (2D) van der Waals (vdW) moiré superlattices and their interlayer interactions have received surging attention after recent discoveries of many new phases of matter that are highly tunable. Different atomistic registry between layers forming the inner and outer nanotubes can also form one-dimensional (1D) vdW moiré superlattices. In this review, experimental observations and theoretical perspectives related to interlayer interactions in 1D vdW moiré superlattices are summarized. The discussion focuses on double-walled carbon nanotubes (DWNTs), a model 1D vdW moiré system, and the authors highlight the new optical features emerging from the non-trivial strong interlayer coupling effect and the unique physics in 1D DWNTs. Future directions and questions in probing the intriguing physical phenomena in 1D vdW moiré superlattices such as, correlated physics in different 1D moiré systems beyond DWNTs are proposed and discussed.
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Affiliation(s)
- Sihan Zhao
- Interdisciplinary Center for Quantum InformationZhejiang Province Key Laboratory of Quantum Technology and DeviceState Key Laboratory of Silicon MaterialsDepartment of PhysicsZhejiang UniversityHangzhou310027China
| | - Ryo Kitaura
- Department of ChemistryNagoya UniversityNagoya464‐8602Japan
| | - Pilkyung Moon
- Arts and SciencesNYU ShanghaiShanghai200122China
- NYU‐ECNU Institute of Physics at NYU ShanghaiShanghai200062China
| | - Mikito Koshino
- Department of PhysicsOsaka UniversityToyonaka560‐0043Japan
| | - Feng Wang
- Department of PhysicsUniversity of California at BerkeleyBerkeleyCA94720USA
- Materials Science DivisionLawrence Berkeley National LaboratoryBerkeleyCAUSA
- Kavli Energy NanoSciences Institute at University of California Berkeley and Lawrence Berkeley National LaboratoryBerkeleyCA94720USA
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18
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Lin KQ, Holler J, Bauer JM, Parzefall P, Scheuck M, Peng B, Korn T, Bange S, Lupton JM, Schüller C. Large-Scale Mapping of Moiré Superlattices by Hyperspectral Raman Imaging. Adv Mater 2021; 33:e2008333. [PMID: 34242447 DOI: 10.1002/adma.202008333] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 05/03/2021] [Indexed: 05/25/2023]
Abstract
Moiré superlattices can induce correlated-electronic phases in twisted van der Waals materials: strongly correlated quantum phenomena emerge, such as superconductivity and the Mott-insulating state. However, moiré superlattices produced through artificial stacking can be quite inhomogeneous, which hampers the development of a clear correlation between the moiré period and the emerging electrical and optical properties. Here, it is demonstrated in twisted-bilayer transition-metal dichalcogenides that low-frequency Raman scattering can be utilized not only to detect atomic reconstruction, but also to map out the inhomogeneity of the moiré lattice over large areas. The method is established based on the finding that both the interlayer-breathing mode and moiré phonons are highly susceptible to the moiré period and provide characteristic fingerprints. Hyperspectral Raman imaging visualizes microscopic domains of a 5° twisted-bilayer sample with an effective twist-angle resolution of about 0.1°. This ambient methodology can be conveniently implemented to characterize and preselect high-quality areas of samples for subsequent device fabrication, and for transport and optical experiments.
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Affiliation(s)
- Kai-Qiang Lin
- Department of Physics, University of Regensburg, 93053, Regensburg, Germany
| | - Johannes Holler
- Department of Physics, University of Regensburg, 93053, Regensburg, Germany
| | - Jonas M Bauer
- Department of Physics, University of Regensburg, 93053, Regensburg, Germany
| | - Philipp Parzefall
- Department of Physics, University of Regensburg, 93053, Regensburg, Germany
| | - Marten Scheuck
- Department of Physics, University of Regensburg, 93053, Regensburg, Germany
| | - Bo Peng
- TCM Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Tobias Korn
- Institute of Physics, University of Rostock, 18059, Rostock, Germany
| | - Sebastian Bange
- Department of Physics, University of Regensburg, 93053, Regensburg, Germany
| | - John M Lupton
- Department of Physics, University of Regensburg, 93053, Regensburg, Germany
| | - Christian Schüller
- Department of Physics, University of Regensburg, 93053, Regensburg, Germany
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19
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Qiu D, Gong C, Wang S, Zhang M, Yang C, Wang X, Xiong J. Recent Advances in 2D Superconductors. Adv Mater 2021; 33:e2006124. [PMID: 33768653 DOI: 10.1002/adma.202006124] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/22/2020] [Indexed: 06/12/2023]
Abstract
The emergence of superconductivity in 2D materials has attracted much attention and there has been rapid development in recent years because of their fruitful physical properties, such as high transition temperature (Tc ), continuous phase transition, and enhanced parallel critical magnetic field (Bc ). Tremendous efforts have been devoted to exploring different physical parameters to figure out the mechanisms behind the unexpected superconductivity phenomena, including adjusting the thickness of samples, fabricating various heterostructures, tuning the carrier density by electric field and chemical doping, and so on. Here, different types of 2D superconductivity with their unique characteristics are introduced, including the conventional Bardeen-Cooper-Schrieffer superconductivity in ultrathin films, high-Tc superconductivity in Fe-based and Cu-based 2D superconductors, unconventional superconductivity in newly discovered twist-angle bilayer graphene, superconductivity with enhanced Bc , and topological superconductivity. A perspective toward this field is then proposed based on academic knowledge from the recently reported literature. The aim is to provide researchers with a clear and comprehensive understanding about the newly developed 2D superconductivity and promote the development of this field much further.
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Affiliation(s)
- Dong Qiu
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Chuanhui Gong
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - SiShuang Wang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Miao Zhang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Chao Yang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Xianfu Wang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Jie Xiong
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
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20
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Ren YN, Lu C, Zhang Y, Li SY, Liu YW, Yan C, Guo ZH, Liu CC, Yang F, He L. Spectroscopic Evidence for a Spin- and Valley-Polarized Metallic State in a Nonmagic-Angle Twisted Bilayer Graphene. ACS Nano 2020; 14:13081-13090. [PMID: 33052664 DOI: 10.1021/acsnano.0c04631] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In the magic-angle twisted bilayer graphene (MA-TBG), strong electron-electron (e-e) correlations caused by the band-flattening lead to many exotic quantum phases such as superconductivity, correlated insulator, ferromagnetism, and quantum anomalous Hall effects, when its low-energy van Hove singularities (VHSs) are partially filled. Here our high-resolution scanning tunneling microscope and spectroscopy measurements demonstrate that the e-e correlation in a nonmagic-angle TBG with a twist angle θ = 1.49° still plays an important role in determining its electronic properties. Our most interesting observation on that sample is when one of its VHSs is partially filled, the one associated peak in the spectrum splits into four peaks. Simultaneously, the spatial symmetry of electronic states around the split VHSs is broken by the e-e correlation. Our analysis based on the continuum model suggests that such a one-to-four split of the VHS originates from the formation of an interaction-driven spin-valley-polarized metallic state near the VHS, which is a symmetry-breaking phase that has not been identified in the MA-TBG or in other systems.
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Affiliation(s)
- Ya-Ning Ren
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Chen Lu
- School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
- School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Yu Zhang
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Si-Yu Li
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
- 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
| | - Yi-Wen Liu
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Chao Yan
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Zi-Han Guo
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Cheng-Cheng Liu
- School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Fan Yang
- School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
| | - Lin He
- Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, People's Republic of China
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21
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Arroyo-Gascón O, Fernández-Perea R, Suárez Morell E, Cabrillo C, Chico L. One-Dimensional Moiré Superlattices and Flat Bands in Collapsed Chiral Carbon Nanotubes. Nano Lett 2020; 20:7588-7593. [PMID: 32870695 DOI: 10.1021/acs.nanolett.0c03091] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We demonstrate that one-dimensional moiré patterns, analogous to those found in twisted bilayer graphene, can arise in collapsed chiral carbon nanotubes. Resorting to a combination of approaches, namely, molecular dynamics to obtain the relaxed geometries and tight-binding calculations validated against ab initio modeling, we find that magic angle physics occur in collapsed carbon nanotubes. Velocity reduction, flat bands, and localization in AA regions with diminishing moiré angle are revealed, showing a magic angle close to 1°. From the spatial extension of the AA regions and the width of the flat bands, we estimate that many-body interactions in these systems are stronger than in twisted bilayer graphene. Chiral collapsed carbon nanotubes stand out as promising candidates to explore many-body effects and superconductivity in low dimensions, emerging as the one-dimensional analogues of twisted bilayer graphene.
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Affiliation(s)
- Olga Arroyo-Gascón
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientı́ficas, C/Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain
| | - Ricardo Fernández-Perea
- Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientı́ficas, Serrano 123, E-28006 Madrid, Spain
| | - Eric Suárez Morell
- Departamento de Fı́sica, Universidad Técnica Federico Santa Marı́a, Casilla 110-V, Valparaı́so, Chile
| | - Carlos Cabrillo
- Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientı́ficas, Serrano 123, E-28006 Madrid, Spain
| | - Leonor Chico
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientı́ficas, C/Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain
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22
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Carr S, Li C, Zhu Z, Kaxiras E, Sachdev S, Kruchkov A. Ultraheavy and Ultrarelativistic Dirac Quasiparticles in Sandwiched Graphenes. Nano Lett 2020; 20:3030-3038. [PMID: 32208724 DOI: 10.1021/acs.nanolett.9b04979] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Electrons in quantum materials exhibiting coexistence of dispersionless (flat) bands piercing dispersive (steep) bands give rise to strongly correlated phenomena and are associated with unconventional superconductivity. We show that in twisted sandwiched graphene (TSWG)-a three-layer van der Waals heterostructure with a twisted middle layer-steep Dirac cones can coexist with dramatic band flattening at the same energy scale, if twisted by 1.5°. This phenomenon is not stable in the simplified continuum models. The key result of this Letter is that the flat bands become stable only as a consequence of lattice relaxation processes included in our atomistic calculations. Further on, external fields can change the relative energy offset between the Dirac cone vertex and the flat bands and enhance band hybridization, which could permit controlling correlated phases. Our work establishes twisted sandwiched graphene as a new platform for research into strongly interacting two-dimensional quantum matter.
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Affiliation(s)
- Stephen Carr
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Chenyuan Li
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Ziyan Zhu
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Efthimios Kaxiras
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
- Harvard J.A. Paulson School of Engineering and Applied Sciences, Cambridge, Massachusetts 02138, United States
| | - Subir Sachdev
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Alexander Kruchkov
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
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