1
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Yu H, Heine T. Prediction of metal-free Stoner and Mott-Hubbard magnetism in triangulene-based two-dimensional polymers. SCIENCE ADVANCES 2024; 10:eadq7954. [PMID: 39356753 DOI: 10.1126/sciadv.adq7954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Accepted: 08/26/2024] [Indexed: 10/04/2024]
Abstract
Ferromagnetism and antiferromagnetism require robust long-range magnetic ordering, which typically involves strongly interacting spins localized at transition metal atoms. However, in metal-free systems, the spin orbitals are largely delocalized, and weak coupling between the spins in the lattice hampers long-range ordering. Metal-free magnetism is of fundamental interest to physical sciences, unlocking unprecedented dimensions for strongly correlated materials and biocompatible magnets. Here, we present a strategy to achieve strong coupling between spin centers of planar radical monomers in π-conjugated two-dimensional (2D) polymers and rationally control the orderings. If the π-states in these triangulene-based 2D polymers are half-occupied, then we predict that they are antiferromagnetic Mott-Hubbard insulators. Incorporating a boron or nitrogen heteroatom per monomer results in Stoner ferromagnetism and half-metallicity, with the Fermi level located at spin-polarized Dirac points. An unprecedented antiferromagnetic half-semiconductor is observed in a binary boron-nitrogen-centered 2D polymer. Our findings pioneer Stoner and Mott-Hubbard magnetism emerging in the electronic π-system of crystalline-conjugated 2D polymers.
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Affiliation(s)
- Hongde Yu
- Faculty of Chemistry and Food Chemistry, TU Dresden, Bergstrasse 66c, 01069 Dresden, Germany
| | - Thomas Heine
- Faculty of Chemistry and Food Chemistry, TU Dresden, Bergstrasse 66c, 01069 Dresden, Germany
- Helmholtz-Zentrum Dresden-Rossendorf, Centrum for Advanced Systems Understanding, CASUS, Untermarkt 20, 02826 Görlitz, Germany
- Department of Chemistry, Yonsei University and IBS Center for Nanomedicine, Seodaemun-gu, Seoul 120-749, Republic of Korea
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2
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Hu ZG, Gao YM, Liu JF, Yang H, Wang M, Lei Y, Zhou X, Li J, Cao X, Liang J, Hu CQ, Li Z, Lau YC, Cai JW, Li BB. Picotesla-sensitivity microcavity optomechanical magnetometry. LIGHT, SCIENCE & APPLICATIONS 2024; 13:279. [PMID: 39341806 PMCID: PMC11439073 DOI: 10.1038/s41377-024-01643-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 09/07/2024] [Accepted: 09/16/2024] [Indexed: 10/01/2024]
Abstract
Cavity optomechanical systems have enabled precision sensing of magnetic fields, by leveraging the optical resonance-enhanced readout and mechanical resonance-enhanced response. Previous studies have successfully achieved mass-produced and reproducible microcavity optomechanical magnetometry (MCOM) by incorporating Terfenol-D thin films into high-quality (Q) factor whispering gallery mode (WGM) microcavities. However, the sensitivity was limited to 585 pT Hz-1/2, over 20 times inferior to those using Terfenol-D particles. In this work, we propose and demonstrate a high-sensitivity and mass-produced MCOM approach by sputtering a FeGaB thin film onto a high-Q SiO2 WGM microdisk. Theoretical studies are conducted to explore the magnetic actuation constant and noise-limited sensitivity by varying the parameters of the FeGaB film and SiO2 microdisk. Multiple magnetometers with different radii are fabricated and characterized. By utilizing a microdisk with a radius of 355 μm and a thickness of 1 μm, along with a FeGaB film with a radius of 330 μm and a thickness of 1.3 μm, we have achieved a remarkable peak sensitivity of 1.68 pT Hz-1/2 at 9.52 MHz. This represents a significant improvement of over two orders of magnitude compared with previous studies employing sputtered Terfenol-D film. Notably, the magnetometer operates without a bias magnetic field, thanks to the remarkable soft magnetic properties of the FeGaB film. Furthermore, as a proof of concept, we have demonstrated the real-time measurement of a pulsed magnetic field simulating the corona current in a high-voltage transmission line using our developed magnetometer. These high-sensitivity magnetometers hold great potential for various applications, such as magnetic induction tomography and corona current monitoring.
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Affiliation(s)
- Zhi-Gang Hu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yi-Meng Gao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jian-Fei Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hao Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Min Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yuechen Lei
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xin Zhou
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jincheng Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physics, Beihang University, Beijing, 100191, China
| | - Xuening Cao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jinjing Liang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chao-Qun Hu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhilin Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory, Dongguan, 523808, Guangdong, China
| | - Yong-Chang Lau
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Jian-Wang Cai
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Bei-Bei Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
- Songshan Lake Materials Laboratory, Dongguan, 523808, Guangdong, China.
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3
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Hassan Y, Singh B, Joe M, Son BM, Ngo TD, Jang Y, Sett S, Singha A, Biswas R, Bhakar M, Watanabe K, Taniguchi T, Raghunathan V, Sheet G, Lee Z, Yoo WJ, Srivastava PK, Lee C. Twist-Controlled Ferroelectricity and Emergent Multiferroicity in WSe 2 Bilayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2406290. [PMID: 39318077 DOI: 10.1002/adma.202406290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Revised: 08/27/2024] [Indexed: 09/26/2024]
Abstract
Recently, researchers have been investigating artificial ferroelectricity, which arises when inversion symmetry is broken in certain R-stacked, i.e., zero-degree twisted, van der Waals (vdW) bilayers. Here, the study reports the twist-controlled ferroelectricity in tungsten diselenide (WSe2) bilayers. The findings show noticeable room temperature ferroelectricity that decreases with twist angle within the range 0° < θ < 3°, and disappears completely for θ ≥ 4°. This variation aligns with moiré length scale-controlled ferroelectric dynamics (0° < θ < 3°), while loss beyond 4° may relate to twist-controlled commensurate to non-commensurate transitions. This twist-controlled ferroelectricity serves as a spectroscopic tool for detecting transitions between commensurate and incommensurate moiré patterns. At 5.5 K, 3° twisted WSe2 exhibits ferroelectric and correlation-driven ferromagnetic ordering, indicating twist-controlled multiferroic behavior. The study offers insights into twist-controlled coexisting ferro-ordering and serves as valuable spectroscopic tools.
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Affiliation(s)
- Yasir Hassan
- Department of Materials Science and Engineering, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 34134, South Korea
| | - Budhi Singh
- School of Mechanical Engineering, Sungkyunkwan University, Suwon, 16419, South Korea
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, South Korea
| | - Minwoong Joe
- School of Mechanical Engineering, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Byoung-Min Son
- Department of Semiconductor Convergence Engineering, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Tien Dat Ngo
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, South Korea
| | - Younggeun Jang
- Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan, 44919, South Korea
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, South Korea
| | - Shaili Sett
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Arup Singha
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Rabindra Biswas
- Department of Electrical and Communication Engineering, Indian Institute of Science, Bangalore, 560012, India
| | - Monika Bhakar
- Department of Physics, Indian Institute of Science Education and Research Mohali, Punjab, 140306, India
| | - Kenji Watanabe
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki, 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki, 305-0044, Japan
| | - Varun Raghunathan
- Department of Electrical and Communication Engineering, Indian Institute of Science, Bangalore, 560012, India
| | - Goutam Sheet
- Department of Physics, Indian Institute of Science Education and Research Mohali, Punjab, 140306, India
| | - Zonghoon Lee
- Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan, 44919, South Korea
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, South Korea
| | - Won Jong Yoo
- SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, South Korea
| | | | - 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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4
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Hesp NCH, Batlle-Porro S, Krishna Kumar R, Agarwal H, Barcons Ruiz D, Herzig Sheinfux H, Watanabe K, Taniguchi T, Stepanov P, Koppens FHL. Cryogenic nano-imaging of second-order moiré superlattices. NATURE MATERIALS 2024:10.1038/s41563-024-01993-y. [PMID: 39256621 DOI: 10.1038/s41563-024-01993-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 08/03/2024] [Indexed: 09/12/2024]
Abstract
Second-order superlattices form when moiré superlattices with similar periodicities interfere with each other, leading to larger superlattice periodicities. These crystalline structures are engineered using two-dimensional materials such as graphene and hexagonal boron nitride, and the specific alignment plays a crucial role in facilitating correlation-driven topological phases. Signatures of second-order superlattices have been identified in magnetotransport experiments; however, real-space visualization is still lacking. Here we reveal the second-order superlattice in magic-angle twisted bilayer graphene closely aligned with hexagonal boron nitride through electronic transport measurements and cryogenic nanoscale photovoltage measurements and evidenced by long-range periodic photovoltage modulations. Our results show that even minuscule strain and twist-angle variations as small as 0.01° can lead to drastic changes in the second-order superlattice structure. Our real-space observations, therefore, serve as a 'magnifying glass' for strain and twist angle and can elucidate the mechanisms responsible for the breaking of spatial symmetries in twisted bilayer graphene.
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Affiliation(s)
- Niels C H Hesp
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - Sergi Batlle-Porro
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - Roshan Krishna Kumar
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - Hitesh Agarwal
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - David Barcons Ruiz
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - Hanan Herzig Sheinfux
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - 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
| | - Petr Stepanov
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain.
- Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN, USA.
- Stavropoulos Center for Complex Quantum Matter, University of Notre Dame, Notre Dame, IN, USA.
| | - Frank H L Koppens
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain.
- ICREA-Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain.
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5
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Xi Y, Shi Z, Zhao M, Cheng N, Du K, Li K, Xu H, Xu S, Liu J, Feng H, Shi Y, Xu X, Hao W, Dou S, Du Y. Modulation of Kondo Behavior in a Two-Dimensional Epitaxial Bilayer Bi(111)/Fe 3GeTe 2 Moiré Heterostructure. ACS NANO 2024; 18:22958-22964. [PMID: 39136292 DOI: 10.1021/acsnano.4c04271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/28/2024]
Abstract
Artificial two-dimensional (2D) moiré superlattices provide a platform for generating exotic quantum matter or phenomena. Here, an epitaxial heterostructure composed of bilayer Bi(111) and an Fe3GeTe2 substrate with a zero-twist angle is acquired by molecular beam epitaxy. Scanning tunneling microscopy and spectroscopy studies reveal the spatially tailored Kondo resonance and interfacial magnetism within this moiré superlattice. Combined with first-principles calculations, it is found that the modulation effect of the moiré superlattice originates from the interfacial orbital hybridization between Bi and Fe atoms. Our work provides a tunable platform for strong electron correlation studies to explore 2D artificial heavy Fermion systems and interface magnetism.
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Affiliation(s)
- Yilian Xi
- School of Physics, Beihang University, Beijing 100191, China
| | - Zhijian Shi
- School of Physics, Beihang University, Beijing 100191, China
| | - Mengting Zhao
- ARC Centre for Future Low Energy Electronics Technologies, Monash University, Clayton, VIC 3800, Australia
| | - Ningyan Cheng
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Leibniz International Joint Research Center of Materials Sciences of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China
| | - Kunrong Du
- School of Physics, Beihang University, Beijing 100191, China
| | - Keren Li
- School of Physics, Beihang University, Beijing 100191, China
| | - Hang Xu
- School of Physics, Beihang University, Beijing 100191, China
| | - Shengjie Xu
- School of Physics, Beihang University, Beijing 100191, China
| | - Jiaqi Liu
- School of Physics, Beihang University, Beijing 100191, China
| | - Haifeng Feng
- School of Physics, Beihang University, Beijing 100191, China
| | - Yan Shi
- School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China
| | - Xun Xu
- Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Wollongong, NSW 2500, Australia
| | - Weichang Hao
- School of Physics, Beihang University, Beijing 100191, China
| | - Shixue Dou
- Instituteof Energy Materials Science (IEMS), University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Yi Du
- School of Physics, Beihang University, Beijing 100191, China
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6
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Wang S, Zhan Z, Fan X, Li Y, Pantaleón PA, Ye C, He Z, Wei L, Li L, Guinea F, Yuan S, Zeng C. Dispersion-Selective Band Engineering in an Artificial Kagome Superlattice. PHYSICAL REVIEW LETTERS 2024; 133:066302. [PMID: 39178462 DOI: 10.1103/physrevlett.133.066302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 04/29/2024] [Accepted: 06/17/2024] [Indexed: 08/25/2024]
Abstract
The relentless pursuit of band structure engineering continues to be a fundamental aspect in solid-state research. Here, we meticulously construct an artificial kagome potential to generate and control multiple Dirac bands of graphene. This unique high-order potential harbors natural multiperiodic components, enabling the reconstruction of band structures through different potential contributions. As a result, the band components, each characterized by distinct dispersions, shift in energy at different velocities in response to the variation of artificial potential. Thereby, we observe a significant spectral weight redistribution of the multiple Dirac peaks. Furthermore, the magnetic field can effectively weaken the superlattice effect and reactivate the intrinsic Dirac band. Overall, we achieve actively dispersion-selective band engineering, a functionality that would substantially increase the freedom in band design.
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Affiliation(s)
- Shuai Wang
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Zhen Zhan
- Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan, Hubei 430072, China
- Imdea Nanoscience, Madrid 28015, Spain
| | - Xiaodong Fan
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yonggang Li
- Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan, Hubei 430072, China
| | | | - Chaochao Ye
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | | | | | - Lin Li
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui 230088, China
| | | | - Shengjun Yuan
- Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan, Hubei 430072, China
- Wuhan Institute of Quantum Technology, Wuhan, Hubei 430206, China
| | - Changgan Zeng
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui 230088, China
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7
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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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8
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Tschudin MA, Broadway DA, Siegwolf P, Schrader C, Telford EJ, Gross B, Cox J, Dubois AEE, Chica DG, Rama-Eiroa R, J G Santos E, Poggio M, Ziebel ME, Dean CR, Roy X, Maletinsky P. Imaging nanomagnetism and magnetic phase transitions in atomically thin CrSBr. Nat Commun 2024; 15:6005. [PMID: 39019853 PMCID: PMC11255258 DOI: 10.1038/s41467-024-49717-9] [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: 03/03/2024] [Accepted: 06/17/2024] [Indexed: 07/19/2024] Open
Abstract
Since their first observation in 2017, atomically thin van der Waals (vdW) magnets have attracted significant fundamental, and application-driven attention. However, their low ordering temperatures, Tc, sensitivity to atmospheric conditions and difficulties in preparing clean large-area samples still present major limitations to further progress, especially amongst van der Waals magnetic semiconductors. The remarkably stable, high-Tc vdW magnet CrSBr has the potential to overcome these key shortcomings, but its nanoscale properties and rich magnetic phase diagram remain poorly understood. Here we use single spin magnetometry to quantitatively characterise saturation magnetization, magnetic anisotropy constants, and magnetic phase transitions in few-layer CrSBr by direct magnetic imaging. We show pristine magnetic phases, devoid of defects on micron length-scales, and demonstrate remarkable air-stability down the monolayer limit. We furthermore address the spin-flip transition in bilayer CrSBr by imaging the phase-coexistence of regions of antiferromagnetically (AFM) ordered and fully aligned spins. Our work will enable the engineering of exotic electronic and magnetic phases in CrSBr and the realization of novel nanomagnetic devices based on this highly promising vdW magnet.
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Affiliation(s)
| | | | | | | | - Evan J Telford
- Department of Physics, Columbia University, New York, NY, USA
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Boris Gross
- Department of Physics, University of Basel, Basel, Switzerland
| | - Jordan Cox
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Adrien E E Dubois
- Department of Physics, University of Basel, Basel, Switzerland
- QNAMI AG, Hofackerstrasse 40 B, Muttenz, CH-4132, Switzerland
| | - Daniel G Chica
- Department of Chemistry, Columbia University, New York, NY, USA
| | - Ricardo Rama-Eiroa
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Basque Country, Spain
- Institute for Condensed Matter Physics and Complex Systems, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, UK
| | - Elton J G Santos
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Basque Country, Spain
- Institute for Condensed Matter Physics and Complex Systems, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, UK
- Higgs Centre for Theoretical Physics, The University of Edinburgh, Edinburgh, EH9 3FD, UK
| | - Martino Poggio
- Department of Physics, University of Basel, Basel, Switzerland
- Swiss Nanoscience Institute, University of Basel, Basel, Switzerland
| | | | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, USA
| | - Xavier Roy
- Department of Chemistry, Columbia University, New York, NY, USA
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9
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Chen M, Xie Y, Cheng B, Yang Z, Li XZ, Chen F, Li Q, Xie J, Watanabe K, Taniguchi T, He WY, Wu M, Liang SJ, Miao F. Selective and quasi-continuous switching of ferroelectric Chern insulator devices for neuromorphic computing. NATURE NANOTECHNOLOGY 2024; 19:962-969. [PMID: 38965346 DOI: 10.1038/s41565-024-01698-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 05/19/2024] [Indexed: 07/06/2024]
Abstract
Quantum materials exhibit dissipationless topological edge state transport with quantized Hall conductance, offering notable potential for fault-tolerant computing technologies. However, the development of topological edge state-based computing devices remains a challenge. Here we report the selective and quasi-continuous ferroelectric switching of topological Chern insulator devices, showcasing a proof-of-concept demonstration in noise-immune neuromorphic computing. We fabricate this ferroelectric Chern insulator device by encapsulating magic-angle twisted bilayer graphene with doubly aligned h-BN layers and observe the coexistence of the interfacial ferroelectricity and the topological Chern insulating states. The observed ferroelectricity exhibits an anisotropic dependence on the in-plane magnetic field. By tuning the amplitude of the gate voltage pulses, we achieve ferroelectric switching between any pair of Chern insulating states in the presence of a finite magnetic field, resulting in 1,280 ferroelectric states with distinguishable Hall resistance levels on a single device. Furthermore, we demonstrate deterministic switching between two arbitrary levels among the record-high number of ferroelectric states. This unique switching capability enables the implementation of a convolutional neural network resistant to external noise, utilizing the quantized Hall conductance levels of the Chern insulator device as weights. Our study provides a promising avenue towards the development of topological quantum neuromorphic computing, where functionality and performance can be drastically enhanced by topological quantum materials.
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Affiliation(s)
- Moyu Chen
- Institute of Brain-Inspired Intelligence, National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Yongqin Xie
- Institute of Brain-Inspired Intelligence, National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Bin Cheng
- Institute of Interdisciplinary Physical Sciences, School of Science, Nanjing University of Science and Technology, Nanjing, China.
| | - Zaizheng Yang
- Institute of Brain-Inspired Intelligence, National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Xin-Zhi Li
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China
| | - Fanqiang Chen
- Institute of Brain-Inspired Intelligence, National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Qiao Li
- Institute of Brain-Inspired Intelligence, National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Jiao Xie
- Institute of Brain-Inspired Intelligence, National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 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
| | - Wen-Yu He
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China
| | - Menghao Wu
- School of Physics and School of Chemistry, Institute of Theoretical Chemistry, Huazhong University of Science and Technology, Wuhan, China
| | - Shi-Jun Liang
- Institute of Brain-Inspired Intelligence, National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China.
| | - Feng Miao
- Institute of Brain-Inspired Intelligence, National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China.
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10
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Sohn J, Lee JM, Lee HW. Dyakonov-Perel-like Orbital and Spin Relaxations in Centrosymmetric Systems. PHYSICAL REVIEW LETTERS 2024; 132:246301. [PMID: 38949365 DOI: 10.1103/physrevlett.132.246301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 05/15/2024] [Indexed: 07/02/2024]
Abstract
The Dyakonov-Perel (DP) mechanism of spin relaxation has long been considered irrelevant in centrosymmetric systems since it was developed originally for noncentrosymmetric ones. We investigate whether this conventional understanding extends to the realm of orbital relaxation, which has recently attracted significant attention. Surprisingly, we find that orbital relaxation in centrosymmetric systems exhibits the DP-like behavior in the weak scattering regime. Moreover, the DP-like orbital relaxation can make the spin relaxation in centrosymmetric systems DP-like through the spin-orbit coupling. We also find that the DP-like orbital and spin relaxations are anisotropic even in materials with high crystal symmetry (such as face-centered cubic structure) and may depend on the orbital and spin nature of electron wave functions.
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11
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Chen Z, Li R, Bai Y, Mao N, Zeer M, Go D, Dai Y, Huang B, Mokrousov Y, Niu C. Topology-Engineered Orbital Hall Effect in Two-Dimensional Ferromagnets. NANO LETTERS 2024. [PMID: 38619844 DOI: 10.1021/acs.nanolett.3c05129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Recent advances in the manipulation of the orbital angular momentum (OAM) within the paradigm of orbitronics presents a promising avenue for the design of future electronic devices. In this context, the recently observed orbital Hall effect (OHE) occupies a special place. Here, focusing on both the second-order topological and quantum anomalous Hall insulators in two-dimensional ferromagnets, we demonstrate that topological phase transitions present an efficient and straightforward way to engineer the OHE, where the OAM distribution can be controlled by the nature of the band inversion. Using first-principles calculations, we identify Janus RuBrCl and three septuple layers of MnBi2Te4 as experimentally feasible examples of the proposed mechanism of OHE engineering by topology. With our work, we open up new possibilities for innovative applications in topological spintronics and orbitronics.
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Affiliation(s)
- Zhiqi Chen
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Runhan Li
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Yingxi Bai
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Ning Mao
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Mahmoud Zeer
- Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany
- Department of Physics, RWTH Aachen University, 52056 Aachen, Germany
| | - Dongwook Go
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
| | - Ying Dai
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Baibiao Huang
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Yuriy Mokrousov
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
| | - Chengwang Niu
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
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12
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Mattiat H, Schneider L, Reiser P, Poggio M, Sahafi P, Jordan A, Budakian R, Averyanov DV, Sokolov IS, Taldenkov AN, Parfenov OE, Kondratev OA, Tokmachev AM, Storchak VG. Mapping the phase-separated state in a 2D magnet. NANOSCALE 2024; 16:5302-5312. [PMID: 38372414 DOI: 10.1039/d3nr06550b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Intrinsic 2D magnets have recently been established as a playground for studies on fundamentals of magnetism, quantum phases, and spintronic applications. The inherent instability at low dimensionality often results in coexistence and/or competition of different magnetic orders. Such instability of magnetic ordering may manifest itself as phase-separated states. In 4f 2D materials, magnetic phase separation is expressed in various experiments; however, the experimental evidence is circumstantial. Here, we employ a high-sensitivity MFM technique to probe the spatial distribution of magnetic states in the paradigmatic 4f 2D ferromagnet EuGe2. Below the ferromagnetic transition temperature, we discover the phase-separated state and follow its evolution with temperature and magnetic field. The characteristic length-scale of magnetic domains amounts to hundreds of nanometers. These observations strongly shape our understanding of the magnetic states in 2D materials at the monolayer limit and contribute to engineering of ultra-compact spintronics.
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Affiliation(s)
- Hinrich Mattiat
- Department of Physics & Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
| | - Lukas Schneider
- Department of Physics & Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
| | - Patrick Reiser
- Department of Physics & Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
| | - Martino Poggio
- Department of Physics & Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland.
| | - Pardis Sahafi
- Department of Physics and Astronomy & Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Andrew Jordan
- Department of Physics and Astronomy & Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Raffi Budakian
- Department of Physics and Astronomy & Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Dmitry V Averyanov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Ivan S Sokolov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Alexander N Taldenkov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Oleg E Parfenov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Oleg A Kondratev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Andrey M Tokmachev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
| | - Vyacheslav G Storchak
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia.
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13
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Hu C, Naik MH, Chan YH, Ruan J, Louie SG. Light-induced shift current vortex crystals in moiré heterobilayers. Proc Natl Acad Sci U S A 2023; 120:e2314775120. [PMID: 38085781 PMCID: PMC10741382 DOI: 10.1073/pnas.2314775120] [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: 08/25/2023] [Accepted: 11/07/2023] [Indexed: 12/24/2023] Open
Abstract
Transition metal dichalcogenide (TMD) moiré superlattices provide an emerging platform to explore various light-induced phenomena. Recently, the discoveries of novel moiré excitons have attracted great interest. The nonlinear optical responses of these systems are however still underexplored. Here, we report investigation of light-induced shift currents (a second-order response generating DC current from optical illumination) in the WSe2/WS2 moiré superlattice. We identify a striking phenomenon of the formation of shift current vortex crystals-i.e., two-dimensional periodic arrays of moiré-scale current vortices and associated magnetic fields with remarkable intensity under laboratory laser setup. Furthermore, we demonstrate high optical tunability of these current vortices-their location, shape, chirality, and magnitude can be tuned by the frequency, polarization, and intensity of the incident light. Electron-hole interactions (excitonic effects) are found to play a crucial role in the generation and nature of the shift current intensity and distribution. Our findings provide a promising all-optical control route to manipulate nanoscale shift current density distributions and magnetic field patterns, as well as shed light on nonlinear optical responses in moiré quantum matter and their possible applications.
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Affiliation(s)
- Chen Hu
- Department of Physics, University of California at Berkeley, Berkeley, CA94720
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Mit H. Naik
- Department of Physics, University of California at Berkeley, Berkeley, CA94720
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Yang-Hao Chan
- Department of Physics, University of California at Berkeley, Berkeley, CA94720
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720
- Institute of Atomic and Molecular Sciences, Academia Sinica, and Physics Division, National Center for Theoretical Sciences, Taipei10617, Taiwan
| | - Jiawei Ruan
- Department of Physics, University of California at Berkeley, Berkeley, CA94720
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720
| | - Steven G. Louie
- Department of Physics, University of California at Berkeley, Berkeley, CA94720
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA94720
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14
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Zhou H, Auerbach N, Uzan M, Zhou Y, Banu N, Zhi W, Huber ME, Watanabe K, Taniguchi T, Myasoedov Y, Yan B, Zeldov E. Imaging quantum oscillations and millitesla pseudomagnetic fields in graphene. Nature 2023; 624:275-281. [PMID: 37993718 PMCID: PMC10719110 DOI: 10.1038/s41586-023-06763-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Accepted: 10/19/2023] [Indexed: 11/24/2023]
Abstract
The exceptional control of the electronic energy bands in atomically thin quantum materials has led to the discovery of several emergent phenomena1. However, at present there is no versatile method for mapping the local band structure in advanced two-dimensional materials devices in which the active layer is commonly embedded in the insulating layers and metallic gates. Using a scanning superconducting quantum interference device, here we image the de Haas-van Alphen quantum oscillations in a model system, the Bernal-stacked trilayer graphene with dual gates, which shows several highly tunable bands2-4. By resolving thermodynamic quantum oscillations spanning more than 100 Landau levels in low magnetic fields, we reconstruct the band structure and its evolution with the displacement field with excellent precision and nanoscale spatial resolution. Moreover, by developing Landau-level interferometry, we show shear-strain-induced pseudomagnetic fields and map their spatial dependence. In contrast to artificially induced large strain, which leads to pseudomagnetic fields of hundreds of tesla5-7, we detect naturally occurring pseudomagnetic fields as low as 1 mT corresponding to graphene twisting by 1 millidegree, two orders of magnitude lower than the typical angle disorder in twisted bilayer graphene8-11. This ability to resolve the local band structure and strain at the nanoscale level enables the characterization and use of tunable band engineering in practical van der Waals devices.
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Affiliation(s)
- Haibiao Zhou
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Nadav Auerbach
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Matan Uzan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Yaozhang Zhou
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Nasrin Banu
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Weifeng Zhi
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Martin E Huber
- Departments of Physics and Electrical Engineering, University of Colorado Denver, Denver, CO, USA
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Yuri Myasoedov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Binghai Yan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Eli Zeldov
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel.
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15
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Parappurath A, Ghawri B, Bhowmik S, Singha A, Watanabe K, Taniguchi T, Ghosh A. Band structure sensitive photoresponse in twisted bilayer graphene proximitized with WSe 2. NANOSCALE 2023; 15:18818-18824. [PMID: 37962416 DOI: 10.1039/d3nr04864k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
The ability to tune the twist angle between different layers of two-dimensional (2D) materials has enabled the creation of electronic flat bands artificially, leading to exotic quantum phases. When a twisted blilayer of graphene (tBLG) is placed at the van der Waals proximity to a semiconducting layer of transition metal dichalcogenide (TMDC), such as WSe2, the emergent phases in the tBLG can fundamentally modify the functionality of such heterostructures. Here we have performed photoresponse measurements in few-layer-WSe2/tBLG heterostructure, where the mis-orientation angle of the tBLG layer was chosen to lie close to the magic angle of 1.1°. Our experiments show that the photoresponse is extremely sensitive to the band structure of tBLG and gets strongly suppressed when the Fermi energy was placed within the low-energy moiré bands. Photoresponse could however be recovered when Fermi energy exceeded the moiré band edge where it was dominated by the photogating effect due to transfer of charge between the tBLG and the WSe2 layers. Our observations suggest the possibility of the screening effects from moiré flat bands that strongly affect the charge transfer process at the WSe2/tBLG interface, which is further supported by time-resolved photo-resistance measurements.
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Affiliation(s)
- Aparna Parappurath
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
| | - Bhaskar Ghawri
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
| | - Saisab Bhowmik
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Arup Singha
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Arindam Ghosh
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore 560 012, India
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16
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Ollier A, Kisiel M, Lu X, Gysin U, Poggio M, Efetov DK, Meyer E. Energy dissipation on magic angle twisted bilayer graphene. COMMUNICATIONS PHYSICS 2023; 6:344. [PMID: 38665414 PMCID: PMC11041686 DOI: 10.1038/s42005-023-01441-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Accepted: 10/26/2023] [Indexed: 04/28/2024]
Abstract
Traditional Joule dissipation omnipresent in today's electronic devices is well understood while the energy loss of the strongly interacting electron systems remains largely unexplored. Twisted bilayer graphene (tBLG) is a host to interaction-driven correlated insulating phases, when the relative rotation is close to the magic angle (1.08∘). We report on low-temperature (5K) nanomechanical energy dissipation of tBLG measured by pendulum atomic force microscopy (p-AFM). The ultrasensitive cantilever tip acting as an oscillating gate over the quantum device shows dissipation peaks attributed to different fractional fillings of the flat energy bands. Local detection allows to determine the twist angle and spatially resolved dissipation images showed the existence of hundred-nanometer domains of different doping. Application of magnetic fields provoked strong oscillations of the dissipation signal at 3/4 band filling, identified in analogy to Aharonov-Bohm oscillations, a wavefunction interference present between domains of different doping and a signature of orbital ferromagnetism.
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Affiliation(s)
- Alexina Ollier
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Swiss Nanoscience Institute, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Marcin Kisiel
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Xiaobo Lu
- International Center for Quantum Materials, Collaborative Innovation Center of Quantum Matter, Peking University, Beijing, 100871 China
| | - Urs Gysin
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Martino Poggio
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Swiss Nanoscience Institute, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Dmitri K. Efetov
- Department of Physics, Ludwig-Maximilians-University München, Geschwister-Scholl-Platz 1, 80539 München, Germany
| | - Ernst Meyer
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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17
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Li X, Wang Z, Lei Z, Ding W, Shi X, Yan J, Ku J. Magnetic characterization techniques and micromagnetic simulations of magnetic nanostructures: from zero to three dimensions. NANOSCALE 2023. [PMID: 37981862 DOI: 10.1039/d3nr04493a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2023]
Abstract
The investigation of the magnetic characteristics of magnetic nanostructures (MNs) in various dimensions is a crucial direction of research in nanomagnetism, with MNs belonging to various dimensions exhibiting magnetic properties related to their geometry. A better understanding of these magnetic properties is required for MN manipulation. The primary tools for researching MNs are magnetic characterisation techniques with great spatial resolution and spin sensitivity. Micromagnetic simulation is another technique that minimises experimental costs, while providing information on the magnetic structure and magnetic behaviour, and has enormous potential for predicting, validating, and extending the magnetic characterisation results. This review first looks at the progress of research into quantitatively characterising the magnetic properties of low-dimensional (including 0D, 1D, and 2D) and 3D MNs in two directions: magnetic characterisation techniques and micromagnetic simulations, with a particular emphasis on the potential for future applications of these techniques. Single magnetic characterization techniques, single micromagnetic simulations, or a mix of both are utilised in these research studies to investigate MNs in a variety of dimensions. How the magnetic characterisation techniques and micromagnetic simulations can be better applied to MNs in various dimensions is then outlined. This discussion has significant application potential for low-dimensional and 3D MNs.
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Affiliation(s)
- Xin Li
- Zijin School of Geology and Mining, Fuzhou University, Fuzhou 350116, China.
- Fujian Key Laboratory of Green Extraction and High-value Utilization of Energy Metals, Fuzhou 350116, China
| | - Zhaolian Wang
- Shandong Huate Magnet Technology Co., Ltd, Weifang 261000, China
| | - Zhongyun Lei
- College of Chemical Engineering, Fuzhou University, Fuzhou 350116, China
| | - Wei Ding
- Zijin School of Geology and Mining, Fuzhou University, Fuzhou 350116, China.
| | - Xiao Shi
- Zijin School of Geology and Mining, Fuzhou University, Fuzhou 350116, China.
| | - Jujian Yan
- Zijin School of Geology and Mining, Fuzhou University, Fuzhou 350116, China.
| | - Jiangang Ku
- Zijin School of Geology and Mining, Fuzhou University, Fuzhou 350116, China.
- Fujian Key Laboratory of Green Extraction and High-value Utilization of Energy Metals, Fuzhou 350116, China
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18
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He M, Cai J, Zhang YH, Liu Y, Li Y, Taniguchi T, Watanabe K, Cobden DH, Yankowitz M, Xu X. Symmetry-Broken Chern Insulators in Twisted Double Bilayer Graphene. NANO LETTERS 2023. [PMID: 37983529 DOI: 10.1021/acs.nanolett.3c03414] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Twisted double bilayer graphene (tDBG) has emerged as a rich platform for studying strongly correlated and topological states, as its flat bands can be continuously tuned by both a perpendicular displacement field and a twist angle. Here, we construct a phase diagram representing the correlated and topological states as a function of these parameters, based on measurements of over a dozen tDBG devices encompassing two distinct stacking configurations. We find a hierarchy of symmetry-broken states that emerge sequentially as the twist angle approaches an apparent optimal value of θ ≈ 1.34°. Nearby this angle, we discover a symmetry-broken Chern insulator (SBCI) state associated with a band filling of 7/2 as well as an incipient SBCI state associated with 11/3 filling. We further observe an anomalous Hall effect at zero field in all samples supporting SBCI states, indicating spontaneous time-reversal symmetry breaking and possible moiré unit cell enlargement at zero magnetic field.
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Affiliation(s)
- Minhao He
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Jiaqi Cai
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Ya-Hui Zhang
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Yang Liu
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Yuhao Li
- Department of Physics, University of Washington, Seattle, Washington 98195, 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
| | - David H Cobden
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
| | - Matthew Yankowitz
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, Washington 98195, United States
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, United States
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19
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Ciorciaro L, Smoleński T, Morera I, Kiper N, Hiestand S, Kroner M, Zhang Y, Watanabe K, Taniguchi T, Demler E, İmamoğlu A. Kinetic magnetism in triangular moiré materials. Nature 2023; 623:509-513. [PMID: 37968525 PMCID: PMC10651480 DOI: 10.1038/s41586-023-06633-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 09/12/2023] [Indexed: 11/17/2023]
Abstract
Magnetic properties of materials ranging from conventional ferromagnetic metals to strongly correlated materials such as cuprates originate from Coulomb exchange interactions. The existence of alternate mechanisms for magnetism that could naturally facilitate electrical control has been discussed theoretically1-7, but an experimental demonstration8 in an extended system has been missing. Here we investigate MoSe2/WS2 van der Waals heterostructures in the vicinity of Mott insulator states of electrons forming a frustrated triangular lattice and observe direct evidence of magnetic correlations originating from a kinetic mechanism. By directly measuring electronic magnetization through the strength of the polarization-selective attractive polaron resonance9,10, we find that when the Mott state is electron-doped, the system exhibits ferromagnetic correlations in agreement with the Nagaoka mechanism.
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Affiliation(s)
- L Ciorciaro
- Institute for Quantum Electronics, ETH Zürich, Zürich, Switzerland
| | - T Smoleński
- Institute for Quantum Electronics, ETH Zürich, Zürich, Switzerland
| | - I Morera
- Departament de Física Quàntica i Astrofísica, Facultat de Física, Universitat de Barcelona, Barcelona, Spain
- Institut de Ciències del Cosmos, Universitat de Barcelona, Barcelona, Spain
| | - N Kiper
- Institute for Quantum Electronics, ETH Zürich, Zürich, Switzerland
| | - S Hiestand
- Institute for Quantum Electronics, ETH Zürich, Zürich, Switzerland
| | - M Kroner
- Institute for Quantum Electronics, ETH Zürich, Zürich, Switzerland
| | - Y Zhang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA
- Min H. Kao Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN, USA
| | - K Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, Japan
| | - T Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - E Demler
- Institute for Theoretical Physics, ETH Zürich, Zürich, Switzerland
| | - A İmamoğlu
- Institute for Quantum Electronics, ETH Zürich, Zürich, Switzerland.
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20
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Yu J, Foutty BA, Kwan YH, Barber ME, Watanabe K, Taniguchi T, Shen ZX, Parameswaran SA, Feldman BE. Spin skyrmion gaps as signatures of strong-coupling insulators in magic-angle twisted bilayer graphene. Nat Commun 2023; 14:6679. [PMID: 37865663 PMCID: PMC10590429 DOI: 10.1038/s41467-023-42275-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 10/05/2023] [Indexed: 10/23/2023] Open
Abstract
The flat electronic bands in magic-angle twisted bilayer graphene (MATBG) host a variety of correlated insulating ground states, many of which are predicted to support charged excitations with topologically non-trivial spin and/or valley skyrmion textures. However, it has remained challenging to experimentally address their ground state order and excitations, both because some of the proposed states do not couple directly to experimental probes, and because they are highly sensitive to spatial inhomogeneities in real samples. Here, using a scanning single-electron transistor, we observe thermodynamic gaps at even integer moiré filling factors at low magnetic fields. We find evidence of a field-tuned crossover from charged spin skyrmions to bare particle-like excitations, suggesting that the underlying ground state belongs to the manifold of strong-coupling insulators. From the spatial dependence of these states and the chemical potential variation within the flat bands, we infer a link between the stability of the correlated ground states and local twist angle and strain. Our work advances the microscopic understanding of the correlated insulators in MATBG and their unconventional excitations.
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Affiliation(s)
- Jiachen Yu
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
- Geballe Laboratory of Advanced Materials, Stanford, CA, 94305, USA
| | - Benjamin A Foutty
- Geballe Laboratory of Advanced Materials, Stanford, CA, 94305, USA
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
| | - Yves H Kwan
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Mark E Barber
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
- Geballe Laboratory of Advanced Materials, Stanford, CA, 94305, USA
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Zhi-Xun Shen
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
- Geballe Laboratory of Advanced Materials, Stanford, CA, 94305, USA
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | | | - Benjamin E Feldman
- Geballe Laboratory of Advanced Materials, Stanford, CA, 94305, USA.
- Department of Physics, Stanford University, Stanford, CA, 94305, USA.
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
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21
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Ferguson GM, Xiao R, Richardella AR, Low D, Samarth N, Nowack KC. Direct visualization of electronic transport in a quantum anomalous Hall insulator. NATURE MATERIALS 2023; 22:1100-1105. [PMID: 37537357 DOI: 10.1038/s41563-023-01622-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 06/26/2023] [Indexed: 08/05/2023]
Abstract
A quantum anomalous Hall (QAH) insulator is characterized by quantized Hall and vanishing longitudinal resistances at zero magnetic field that are protected against local perturbations and independent of sample details. This insensitivity makes the microscopic details of the local current distribution inaccessible to global transport measurements. Accordingly, the current distributions that give rise to transport quantization are unknown. Here we use magnetic imaging to directly visualize the transport current in the QAH regime. As we tune through the QAH plateau by electrostatic gating, we clearly identify a regime in which the sample transports current primarily in the bulk rather than along the edges. Furthermore, we image the local response of equilibrium magnetization to electrostatic gating. Combined, these measurements suggest that the current flows through incompressible regions whose spatial structure can change throughout the QAH regime. Identification of the appropriate microscopic picture of electronic transport in QAH insulators and other topologically non-trivial states of matter is a crucial step towards realizing their potential in next-generation quantum devices.
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Affiliation(s)
- G M Ferguson
- Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, NY, USA
| | - Run Xiao
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, USA
| | - Anthony R Richardella
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, USA
| | - David Low
- Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, NY, USA
| | - Nitin Samarth
- Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, PA, USA
| | - Katja C Nowack
- Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY, USA.
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22
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Bhowmik S, Ghawri B, Park Y, Lee D, Datta S, Soni R, Watanabe K, Taniguchi T, Ghosh A, Jung J, Chandni U. Spin-orbit coupling-enhanced valley ordering of malleable bands in twisted bilayer graphene on WSe 2. Nat Commun 2023; 14:4055. [PMID: 37422470 DOI: 10.1038/s41467-023-39855-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 06/26/2023] [Indexed: 07/10/2023] Open
Abstract
Recent experiments in magic-angle twisted bilayer graphene have revealed a wealth of novel electronic phases as a result of interaction-driven spin-valley flavour polarisation. In this work, we investigate correlated phases due to the combined effect of spin-orbit coupling-enhanced valley polarisation and the large density of states below half filling of the moiré band in twisted bilayer graphene coupled to tungsten diselenide. We observe an anomalous Hall effect, accompanied by a series of Lifshitz transitions that are highly tunable with carrier density and magnetic field. The magnetisation shows an abrupt change of sign near half-filling, confirming its orbital nature. While the Hall resistance is not quantised at zero magnetic fields-indicating a ground state with partial valley polarisation-perfect quantisation and complete valley polarisation are observed at finite fields. Our results illustrate that singularities in the flat bands in the presence of spin-orbit coupling can stabilise ordered phases even at non-integer moiré band fillings.
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Affiliation(s)
- Saisab Bhowmik
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore, 560012, India.
| | - Bhaskar Ghawri
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Youngju Park
- Department of Physics, University of Seoul, Seoul, 02504, Korea
| | - Dongkyu Lee
- Department of Physics, University of Seoul, Seoul, 02504, Korea
- Department of Smart Cities, University of Seoul, Seoul, 02504, Korea
| | - Suvronil Datta
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Radhika Soni
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore, 560012, India
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki, 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki, 305-0044, Japan
| | - 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
| | - Jeil Jung
- Department of Physics, University of Seoul, Seoul, 02504, Korea.
- Department of Smart Cities, University of Seoul, Seoul, 02504, Korea.
| | - U Chandni
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore, 560012, India.
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23
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Perpendicular electric field drives Chern transitions and layer polarization changes in Hofstadter bands. Nat Commun 2022; 13:7781. [PMID: 36526625 PMCID: PMC9758152 DOI: 10.1038/s41467-022-35421-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 12/02/2022] [Indexed: 12/23/2022] Open
Abstract
Moiré superlattices engineer band properties and enable observation of fractal energy spectra of Hofstadter butterfly. Recently, correlated-electron physics hosted by flat bands in small-angle moiré systems has been at the foreground. However, the implications of moiré band topology within the single-particle framework are little explored experimentally. An outstanding problem is understanding the effect of band topology on Hofstadter physics, which does not require electron correlations. Our work experimentally studies Chern state switching in the Hofstadter regime using twisted double bilayer graphene (TDBG), which offers electric field tunable topological bands, unlike twisted bilayer graphene. Here we show that the nontrivial topology reflects in the Hofstadter spectra, in particular, by displaying a cascade of Hofstadter gaps that switch their Chern numbers sequentially while varying the perpendicular electric field. Our experiments together with theoretical calculations suggest a crucial role of charge polarization changing concomitantly with topological transitions in this system. Layer polarization is likely to play an important role in the topological states in few-layer twisted systems. Moreover, our work establishes TDBG as a novel Hofstadter platform with nontrivial magnetoelectric coupling.
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24
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Spontaneous time-reversal symmetry breaking in twisted double bilayer graphene. Nat Commun 2022; 13:6468. [PMID: 36309518 PMCID: PMC9617879 DOI: 10.1038/s41467-022-34192-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 10/12/2022] [Indexed: 11/08/2022] Open
Abstract
Twisted double bilayer graphene (tDBG) comprises two Bernal-stacked bilayer graphene sheets with a twist between them. Gate voltages applied to top and back gates of a tDBG device tune both the flatness and topology of the electronic bands, enabling an unusual level of experimental control. Metallic states with broken spin and valley symmetries have been observed in tDBG devices with twist angles in the range 1.2–1.3°, but the topologies and order parameters of these states have remained unclear. We report the observation of an anomalous Hall effect in the correlated metal state of tDBG, with hysteresis loops spanning hundreds of mT in out-of-plane magnetic field (B⊥) that demonstrate spontaneously broken time-reversal symmetry. The B⊥ hysteresis persists for in-plane fields up to several Tesla, suggesting valley (orbital) ferromagnetism. At the same time, the resistivity is strongly affected by even mT-scale values of in-plane magnetic field, pointing to spin-valley coupling or to a direct orbital coupling between in-plane field and the valley degree of freedom. Twisted double bilayer graphene (tDBG) comprises two Bernal-stacked bilayer graphene sheets with a twist between them. Here, the authors report a strong anomalous Hall effect in the correlated-metal regime of tDBG, indicating time reversal symmetry breaking from orbital ferromagnetism, likely associated with valley polarization.
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25
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Goodwin ZAH, Fal'ko VI. Moiré modulation of charge density waves. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:494001. [PMID: 36223792 DOI: 10.1088/1361-648x/ac99ca] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 10/12/2022] [Indexed: 06/16/2023]
Abstract
Here we investigate how charge density waves (CDWs), inherent to a monolayer, are effected by creating twisted van der Waals structures. Homobilayers of metallic transition metal dichalcogenides (TMDs), at small twist angles where there is significant atomic reconstruction, are utilised as an example to investigate the interplay between the moiré domain structure and CDWs of different periods. For3×3CDWs, there is no geometric constraint to prevent the CDWs from propagating throughout the moiré structure. Whereas for2×2CDWs, to ensure the CDWs in each layer have the most favourable interactions in the domains, the CDW phase must be destroyed in the connecting domain walls. For3×3CDWs with twist angles close to 180∘, moiré-scale triangular structures can form; while close to 0∘, moiré-scale dimer domains occur. The star-of-David CDW (13×13) is found to host CDWs in the domains only, since there is one low energy stacking configuration, similar to the2×2CDWs. These predictions are offered for experimental verification in twisted bilayer metallic TMDs which host CDWs, and we hope this will stimulate further research on the interplay between the moiré superlattice and CDW phases intrinsic to the comprising 2D materials.
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Affiliation(s)
- Zachary A H Goodwin
- National Graphene Institute, University of Manchester, Booth St. E., Manchester M13 9PL, United Kingdom
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Vladimir I Fal'ko
- National Graphene Institute, University of Manchester, Booth St. E., Manchester M13 9PL, United Kingdom
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- Henry Royce Institute for Advanced Materials, University of Manchester, Manchester M13 9PL, United Kingdom
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26
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Yin JX, Jiang YX, Teng X, Hossain MS, Mardanya S, Chang TR, Ye Z, Xu G, Denner MM, Neupert T, Lienhard B, Deng HB, Setty C, Si Q, Chang G, Guguchia Z, Gao B, Shumiya N, Zhang Q, Cochran TA, Multer D, Yi M, Dai P, Hasan MZ. Discovery of Charge Order and Corresponding Edge State in Kagome Magnet FeGe. PHYSICAL REVIEW LETTERS 2022; 129:166401. [PMID: 36306757 DOI: 10.1103/physrevlett.129.166401] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 09/14/2022] [Indexed: 06/16/2023]
Abstract
Kagome materials often host exotic quantum phases, including spin liquids, Chern gap, charge density wave, and superconductivity. Existing scanning microscopy studies of the kagome charge order have been limited to nonkagome surface layers. Here, we tunnel into the kagome lattice of FeGe to uncover features of the charge order. Our spectroscopic imaging identifies a 2×2 charge order in the magnetic kagome lattice, resembling that discovered in kagome superconductors. Spin mapping across steps of unit cell height demonstrates the existence of spin-polarized electrons with an antiferromagnetic stacking order. We further uncover the correlation between antiferromagnetism and charge order anisotropy, highlighting the unusual magnetic coupling of the charge order. Finally, we detect a pronounced edge state within the charge order energy gap, which is robust against the irregular shape fluctuations of the kagome lattice edges. We discuss our results with the theoretically considered topological features of the kagome charge order including unconventional magnetism and bulk-boundary correspondence.
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Affiliation(s)
- Jia-Xin Yin
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Yu-Xiao Jiang
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Xiaokun Teng
- Department of Physics and Astronomy, Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
| | - Md Shafayat Hossain
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Sougata Mardanya
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
| | - Tay-Rong Chang
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
| | - Zijin Ye
- Wuhan National High Magnetic Field Center & School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Gang Xu
- Wuhan National High Magnetic Field Center & School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - M Michael Denner
- Department of Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Titus Neupert
- Department of Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Benjamin Lienhard
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Han-Bin Deng
- Laboratory for Quantum Emergence, department of physics, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Chandan Setty
- Department of Physics and Astronomy, Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
| | - Qimiao Si
- Department of Physics and Astronomy, Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
| | - Guoqing Chang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 639798, Singapore
| | - Zurab Guguchia
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Bin Gao
- Department of Physics and Astronomy, Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
| | - Nana Shumiya
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Qi Zhang
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Tyler A Cochran
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Daniel Multer
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Ming Yi
- Department of Physics and Astronomy, Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
| | - Pengcheng Dai
- Department of Physics and Astronomy, Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
| | - M Zahid Hasan
- Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, USA
- Quantum Science Center, Oak Ridge, Tennessee 37830, USA
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27
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Control of chiral orbital currents in a colossal magnetoresistance material. Nature 2022; 611:467-472. [PMID: 36224383 DOI: 10.1038/s41586-022-05262-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 08/22/2022] [Indexed: 11/08/2022]
Abstract
Colossal magnetoresistance (CMR) is an extraordinary enhancement of the electrical conductivity in the presence of a magnetic field. It is conventionally associated with a field-induced spin polarization that drastically reduces spin scattering and electric resistance. Ferrimagnetic Mn3Si2Te6 is an intriguing exception to this rule: it exhibits a seven-order-of-magnitude reduction in ab plane resistivity that occurs only when a magnetic polarization is avoided1,2. Here, we report an exotic quantum state that is driven by ab plane chiral orbital currents (COC) flowing along edges of MnTe6 octahedra. The c axis orbital moments of ab plane COC couple to the ferrimagnetic Mn spins to drastically increase the ab plane conductivity (CMR) when an external magnetic field is aligned along the magnetic hard c axis. Consequently, COC-driven CMR is highly susceptible to small direct currents exceeding a critical threshold, and can induce a time-dependent, bistable switching that mimics a first-order 'melting transition' that is a hallmark of the COC state. The demonstrated current-control of COC-enabled CMR offers a new paradigm for quantum technologies.
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28
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Koh JM, Tai T, Lee CH. Simulation of Interaction-Induced Chiral Topological Dynamics on a Digital Quantum Computer. PHYSICAL REVIEW LETTERS 2022; 129:140502. [PMID: 36240412 DOI: 10.1103/physrevlett.129.140502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Revised: 06/30/2022] [Accepted: 09/02/2022] [Indexed: 06/16/2023]
Abstract
Chiral edge states are highly sought after as paradigmatic topological states relevant to both quantum information processing and dissipationless electron transport. Using superconducting transmon-based quantum computers, we demonstrate chiral topological propagation that is induced by suitably designed interactions, instead of flux or spin-orbit coupling. Also different from conventional 2D realizations, our effective Chern lattice is implemented on a much smaller equivalent 1D spin chain, with sequences of entangling gates encapsulating the required time-reversal breaking. By taking advantage of the quantum nature of the platform, we circumvented difficulties from the limited qubit number and gate fidelity in present-day noisy intermediate-scale quantum era quantum computers, paving the way for the quantum simulation of more sophisticated topological states on very rapidly developing quantum hardware.
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Affiliation(s)
- Jin Ming Koh
- Division of Physics, Mathematics and Astronomy, Caltech, Pasadena, California 91125, USA
| | - Tommy Tai
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
- Department of Physics, National University of Singapore, Singapore 117542
| | - Ching Hua Lee
- Department of Physics, National University of Singapore, Singapore 117542
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29
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Hong JP, Soejima T, Zaletel MP. Detecting Symmetry Breaking in Magic Angle Graphene Using Scanning Tunneling Microscopy. PHYSICAL REVIEW LETTERS 2022; 129:147001. [PMID: 36240422 DOI: 10.1103/physrevlett.129.147001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 08/20/2022] [Accepted: 08/25/2022] [Indexed: 06/16/2023]
Abstract
A growing body of experimental work suggests that magic angle twisted bilayer graphene exhibits a "cascade" of spontaneous symmetry-breaking transitions, sparking interest in the potential relationship between symmetry breaking and superconductivity. However, it has proven difficult to find experimental probes which can unambiguously identify the nature of the symmetry breaking. Here, we show how atomically resolved scanning tunneling microscopy can be used as a fingerprint of symmetry-breaking order. By analyzing the pattern of sublattice polarization and "Kekulé" distortions in small magnetic fields, order parameters for each of the most competitive symmetry-breaking states can be identified. In particular, we show that the "Kramers intervalley coherent state," which theoretical work predicts to be the ground state at even integer fillings, shows a Kekulé distortion which emerges only in a magnetic field.
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Affiliation(s)
- Jung Pyo Hong
- Department of Physics, Princeton University, Princeton, New Jersey 08540, USA
| | - Tomohiro Soejima
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Michael P Zaletel
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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30
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Salvato M, Crescenzi MD, Scagliotti M, Castrucci P, Boninelli S, Caruso GM, Liu Y, Mikkelsen A, Timm R, Nahas S, Black-Schaffer A, Kunakova G, Andzane J, Erts D, Bauch T, Lombardi F. Nanometric Moiré Stripes on the Surface of Bi 2Se 3 Topological Insulator. ACS NANO 2022; 16:13860-13868. [PMID: 36098662 PMCID: PMC9527797 DOI: 10.1021/acsnano.2c02515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Accepted: 09/07/2022] [Indexed: 06/15/2023]
Abstract
Mismatch between adjacent atomic layers in low-dimensional materials, generating moiré patterns, has recently emerged as a suitable method to tune electronic properties by inducing strong electron correlations and generating novel phenomena. Beyond graphene, van der Waals structures such as three-dimensional (3D) topological insulators (TIs) appear as ideal candidates for the study of these phenomena due to the weak coupling between layers. Here we discover and investigate the origin of 1D moiré stripes on the surface of Bi2Se3 TI thin films and nanobelts. Scanning tunneling microscopy and high-resolution transmission electron microscopy reveal a unidirectional strained top layer, in the range 14-25%, with respect to the relaxed bulk structure, which cannot be ascribed to the mismatch with the substrate lattice but rather to strain induced by a specific growth mechanism. The 1D stripes are characterized by a spatial modulation of the local density of states, which is strongly enhanced compared to the bulk system. Density functional theory calculations confirm the experimental findings, showing that the TI surface Dirac cone is preserved in the 1D moiré stripes, as expected from the topology, though with a heavily renormalized Fermi velocity that also changes between the top and valley of the stripes. The strongly enhanced density of surface states in the TI 1D moiré superstructure can be instrumental in promoting strong correlations in the topological surface states, which can be responsible for surface magnetism and topological superconductivity.
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Affiliation(s)
- Matteo Salvato
- Dipartimento
di Fisica and INFN, Università di
Roma “Tor Vergata”, 00133 Roma, Italy
| | - Maurizio De Crescenzi
- Dipartimento
di Fisica and INFN, Università di
Roma “Tor Vergata”, 00133 Roma, Italy
| | - Mattia Scagliotti
- Dipartimento
di Fisica and INFN, Università di
Roma “Tor Vergata”, 00133 Roma, Italy
| | - Paola Castrucci
- Dipartimento
di Fisica and INFN, Università di
Roma “Tor Vergata”, 00133 Roma, Italy
| | | | | | - Yi Liu
- Division
of Synchrotron Radiation Research, Department of Physics and NanoLund, Lund University, 221 00 Lund, Sweden
| | - Anders Mikkelsen
- Division
of Synchrotron Radiation Research, Department of Physics and NanoLund, Lund University, 221 00 Lund, Sweden
| | - Rainer Timm
- Division
of Synchrotron Radiation Research, Department of Physics and NanoLund, Lund University, 221 00 Lund, Sweden
| | - Suhas Nahas
- Department
of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
| | - Annica Black-Schaffer
- Department
of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
| | - Gunta Kunakova
- Institute
of Chemical Physics, University of Latvia, LV-1586 Riga, Latvia
- Quantum Device
Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Goteborg, Sweden
| | - Jana Andzane
- Institute
of Chemical Physics, University of Latvia, LV-1586 Riga, Latvia
| | - Donats Erts
- Institute
of Chemical Physics, University of Latvia, LV-1586 Riga, Latvia
| | - Thilo Bauch
- Quantum Device
Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Goteborg, Sweden
| | - Floriana Lombardi
- Quantum Device
Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Goteborg, Sweden
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31
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Călugăru D, Regnault N, Oh M, Nuckolls KP, Wong D, Lee RL, Yazdani A, Vafek O, Bernevig BA. Spectroscopy of Twisted Bilayer Graphene Correlated Insulators. PHYSICAL REVIEW LETTERS 2022; 129:117602. [PMID: 36154402 DOI: 10.1103/physrevlett.129.117602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 07/13/2022] [Indexed: 06/16/2023]
Abstract
We analytically compute the scanning tunneling microscopy (STM) signatures of integer-filled correlated ground states of the magic angle twisted bilayer graphene (TBG) narrow bands. After experimentally validating the strong-coupling approach at ±4 electrons/moiré unit cell, we consider the spatial features of the STM signal for 14 different many-body correlated states and assess the possibility of Kekulé distortion (KD) emerging at the graphene lattice scale. Remarkably, we find that coupling the two opposite graphene valleys in the intervalley-coherent (IVC) TBG insulators does not always result in KD. As an example, we show that the Kramers IVC state and its nonchiral U(4) rotations do not exhibit any KD, while the time-reversal-symmetric IVC state does. Our results, obtained over a large range of energies and model parameters, show that the STM signal and Chern number of a state can be used to uniquely determine the nature of the TBG ground state.
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Affiliation(s)
- Dumitru Călugăru
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Nicolas Regnault
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Myungchul Oh
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Kevin P Nuckolls
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Dillon Wong
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Ryan L Lee
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Ali Yazdani
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Oskar Vafek
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
| | - B Andrei Bernevig
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
- Donostia International Physics Center, P. Manuel de Lardizabal 4, 20018 Donostia-San Sebastian, Spain
- IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Spain
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32
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Huxter WS, Palm ML, Davis ML, Welter P, Lambert CH, Trassin M, Degen CL. Scanning gradiometry with a single spin quantum magnetometer. Nat Commun 2022; 13:3761. [PMID: 35768430 PMCID: PMC9243102 DOI: 10.1038/s41467-022-31454-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 06/16/2022] [Indexed: 12/03/2022] Open
Abstract
Quantum sensors based on spin defects in diamond have recently enabled detailed imaging of nanoscale magnetic patterns, such as chiral spin textures, two-dimensional ferromagnets, or superconducting vortices, based on a measurement of the static magnetic stray field. Here, we demonstrate a gradiometry technique that significantly enhances the measurement sensitivity of such static fields, leading to new opportunities in the imaging of weakly magnetic systems. Our method relies on the mechanical oscillation of a single nitrogen-vacancy center at the tip of a scanning diamond probe, which up-converts the local spatial gradients into ac magnetic fields enabling the use of sensitive ac quantum protocols. We show that gradiometry provides important advantages over static field imaging: (i) an order-of-magnitude better sensitivity, (ii) a more localized and sharper image, and (iii) a strong suppression of field drifts. We demonstrate the capabilities of gradiometry by imaging the nanotesla fields appearing above topographic defects and atomic steps in an antiferromagnet, direct currents in a graphene device, and para- and diamagnetic metals.
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Affiliation(s)
- W S Huxter
- Department of Physics, ETH Zurich, Otto Stern Weg 1, 8093, Zurich, Switzerland
| | - M L Palm
- Department of Physics, ETH Zurich, Otto Stern Weg 1, 8093, Zurich, Switzerland
| | - M L Davis
- Department of Physics, ETH Zurich, Otto Stern Weg 1, 8093, Zurich, Switzerland
| | - P Welter
- Department of Physics, ETH Zurich, Otto Stern Weg 1, 8093, Zurich, Switzerland
| | - C-H Lambert
- Department of Materials, ETH Zurich, Hönggerbergring 64, 8093, Zurich, Switzerland
| | - M Trassin
- Department of Materials, ETH Zurich, Vladimir Prelog Weg 1-5/10, 8093, Zurich, Switzerland
| | - C L Degen
- Department of Physics, ETH Zurich, Otto Stern Weg 1, 8093, Zurich, Switzerland.
- Quantum Center, ETH Zurich, 8093, Zurich, Switzerland.
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33
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Li Y, Xie X, Li B, Sun X, Yang Y, Liu J, Feng J, Zhou Y, Li Y, Liu W, Wang S, Wang W, Zeng H, Zhang Z, Shen D, Shen D. Directed exfoliating and ordered stacking of transition-metal-dichalcogenides. NANOSCALE 2022; 14:7484-7492. [PMID: 35471207 DOI: 10.1039/d1nr07688d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Two-dimensional van der Waals crystals provide a limitless scope for designing novel combinations of physical properties by controlling the stacking order or twist angle of individual layers. Lattice orientation between stacked monolayers is significant not only for breaking the engineering symmetry but also for the study of many-body quantum phases and band topology. Thus far the state-of-the-art exfoliation approaches focus on the achievements of quality, size, yield, and scalability, while lacking sufficient information on lattice orientation. Consequently, interlayer alignment is usually determined by later experiments, such as the second harmonic generation spectroscopy, which increase the number of trials and errors for a designed artificial ordering and hampered the efficiency of systematic study. Herein, we report a lattice orientation distinguishable exfoliation method via gold favor epitaxy along the specific atomic step edges, meanwhile, fulfilling the requirements of high-quality, large-size, and high-yield monolayers. Hexagonal- and rhombohedral-stacking configurations of bilayer transition metal dichalcogenides are built directly at once as a result of foreseeing the lattice orientation. Optical spectroscopy, electron diffraction, and angle-resolved photoemission spectroscopy are used to study crystal quality, symmetric breaking, and band tuning, which support the exfoliating mechanism we proposed. This strategy shows the ability to facilitate the development of ordering stacking especially for multilayers assembling in the future.
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Affiliation(s)
- Yanshuang Li
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, No. 3888 Dongnanhu Road, Changchun, 130033, People's Republic of China.
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Xiuhua Xie
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, No. 3888 Dongnanhu Road, Changchun, 130033, People's Republic of China.
| | - Binghui Li
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, No. 3888 Dongnanhu Road, Changchun, 130033, People's Republic of China.
| | - Xiaoli Sun
- Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China.
| | - Yichen Yang
- Center for Excellence in Superconducting Electronics, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.
| | - Jishan Liu
- Center for Excellence in Superconducting Electronics, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiying Feng
- Key Laboratory of UV-Emitting Materials and Technology, Ministry of Education, Northeast Normal University, Changchun 130024, China
| | - Ying Zhou
- Key Laboratory of UV-Emitting Materials and Technology, Ministry of Education, Northeast Normal University, Changchun 130024, China
| | - Yuanzheng Li
- Key Laboratory of UV-Emitting Materials and Technology, Ministry of Education, Northeast Normal University, Changchun 130024, China
| | - Weizhen Liu
- Key Laboratory of UV-Emitting Materials and Technology, Ministry of Education, Northeast Normal University, Changchun 130024, China
| | - Shuangpeng Wang
- MOE Joint Key Laboratory, Institute of Applied Physics and Materials Engineering and Department of Physics and Chemistry, Faculty of Science and Technology, University of Macau, Macao SAR 999078, P. R. China
| | - Wei Wang
- MOE Joint Key Laboratory, Institute of Applied Physics and Materials Engineering and Department of Physics and Chemistry, Faculty of Science and Technology, University of Macau, Macao SAR 999078, P. R. China
| | - Huan Zeng
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, No. 3888 Dongnanhu Road, Changchun, 130033, People's Republic of China.
- University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Zhenzhong Zhang
- School of Microelectronics, Dalian University of Technology, Dalian, 116024, China
| | - Dawei Shen
- Center for Excellence in Superconducting Electronics, State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.
| | - Dezhen Shen
- State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, No. 3888 Dongnanhu Road, Changchun, 130033, People's Republic of China.
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34
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Wang QH, Bedoya-Pinto A, Blei M, Dismukes AH, Hamo A, Jenkins S, Koperski M, Liu Y, Sun QC, Telford EJ, Kim HH, Augustin M, Vool U, Yin JX, Li LH, Falin A, Dean CR, Casanova F, Evans RFL, Chshiev M, Mishchenko A, Petrovic C, He R, Zhao L, Tsen AW, Gerardot BD, Brotons-Gisbert M, Guguchia Z, Roy X, Tongay S, Wang Z, Hasan MZ, Wrachtrup J, Yacoby A, Fert A, Parkin S, Novoselov KS, Dai P, Balicas L, Santos EJG. The Magnetic Genome of Two-Dimensional van der Waals Materials. ACS NANO 2022; 16:6960-7079. [PMID: 35442017 PMCID: PMC9134533 DOI: 10.1021/acsnano.1c09150] [Citation(s) in RCA: 70] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 02/23/2022] [Indexed: 05/23/2023]
Abstract
Magnetism in two-dimensional (2D) van der Waals (vdW) materials has recently emerged as one of the most promising areas in condensed matter research, with many exciting emerging properties and significant potential for applications ranging from topological magnonics to low-power spintronics, quantum computing, and optical communications. In the brief time after their discovery, 2D magnets have blossomed into a rich area for investigation, where fundamental concepts in magnetism are challenged by the behavior of spins that can develop at the single layer limit. However, much effort is still needed in multiple fronts before 2D magnets can be routinely used for practical implementations. In this comprehensive review, prominent authors with expertise in complementary fields of 2D magnetism (i.e., synthesis, device engineering, magneto-optics, imaging, transport, mechanics, spin excitations, and theory and simulations) have joined together to provide a genome of current knowledge and a guideline for future developments in 2D magnetic materials research.
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Affiliation(s)
- Qing Hua Wang
- Materials
Science and Engineering, School for Engineering of Matter, Transport
and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Amilcar Bedoya-Pinto
- NISE
Department, Max Planck Institute of Microstructure
Physics, 06120 Halle, Germany
- Instituto
de Ciencia Molecular (ICMol), Universitat
de València, 46980 Paterna, Spain
| | - Mark Blei
- Materials
Science and Engineering, School for Engineering of Matter, Transport
and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Avalon H. Dismukes
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Assaf Hamo
- Department
of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Sarah Jenkins
- Twist
Group,
Faculty of Physics, University of Duisburg-Essen, Campus Duisburg, 47057 Duisburg, Germany
| | - Maciej Koperski
- Institute
for Functional Intelligent Materials, National
University of Singapore, 117544 Singapore
| | - Yu Liu
- Condensed
Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Qi-Chao Sun
- Physikalisches
Institut, University of Stuttgart, 70569 Stuttgart, Germany
| | - Evan J. Telford
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Hyun Ho Kim
- School
of Materials Science and Engineering, Department of Energy Engineering
Convergence, Kumoh National Institute of
Technology, Gumi 39177, Korea
| | - Mathias Augustin
- Institute
for Condensed Matter Physics and Complex Systems, School of Physics
and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
- Donostia
International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
| | - Uri Vool
- Department
of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
- John Harvard
Distinguished Science Fellows Program, Harvard
University, Cambridge, Massachusetts 02138, United States
| | - Jia-Xin Yin
- Laboratory
for Topological Quantum Matter and Spectroscopy, Department of Physics, Princeton University, Princeton, New Jersey 08544, United States
| | - Lu Hua Li
- Institute
for Frontier Materials, Deakin University, Geelong Waurn Ponds Campus, Waurn Ponds, Victoria 3216, Australia
| | - Alexey Falin
- Institute
for Frontier Materials, Deakin University, Geelong Waurn Ponds Campus, Waurn Ponds, Victoria 3216, Australia
| | - Cory R. Dean
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Fèlix Casanova
- CIC nanoGUNE
BRTA, 20018 Donostia - San Sebastián, Basque
Country, Spain
- IKERBASQUE,
Basque Foundation for Science, 48013 Bilbao, Basque Country, Spain
| | - Richard F. L. Evans
- Department
of Physics, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Mairbek Chshiev
- Université
Grenoble Alpes, CEA, CNRS, Spintec, 38000 Grenoble, France
- Institut
Universitaire de France, 75231 Paris, France
| | - Artem Mishchenko
- Department
of Physics and Astronomy, University of
Manchester, Manchester, M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Cedomir Petrovic
- Condensed
Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Rui He
- Department
of Electrical and Computer Engineering, Texas Tech University, 910 Boston Avenue, Lubbock, Texas 79409, United
States
| | - Liuyan Zhao
- Department
of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109, United States
| | - Adam W. Tsen
- Institute
for Quantum Computing and Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Brian D. Gerardot
- SUPA, Institute
of Photonics and Quantum Sciences, Heriot-Watt
University, Edinburgh EH14 4AS, United Kingdom
| | - Mauro Brotons-Gisbert
- SUPA, Institute
of Photonics and Quantum Sciences, Heriot-Watt
University, Edinburgh EH14 4AS, United Kingdom
| | - Zurab Guguchia
- Laboratory
for Muon Spin Spectroscopy, Paul Scherrer
Institute, CH-5232 Villigen PSI, Switzerland
| | - Xavier Roy
- Department
of Chemistry, Columbia University, New York, New York 10027, United States
| | - Sefaattin Tongay
- Materials
Science and Engineering, School for Engineering of Matter, Transport
and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Ziwei Wang
- Department
of Physics and Astronomy, University of
Manchester, Manchester, M13 9PL, United Kingdom
- National
Graphene Institute, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - M. Zahid Hasan
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Princeton
Institute for Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, United States
- National
High Magnetic Field Laboratory, Florida
State University, Tallahassee, Florida 32310, United States
| | - Joerg Wrachtrup
- Physikalisches
Institut, University of Stuttgart, 70569 Stuttgart, Germany
- Max Planck
Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Amir Yacoby
- Department
of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
- John A.
Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Albert Fert
- Donostia
International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
- Unité
Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
- Department
of Materials Physics UPV/EHU, 20018 Donostia - San Sebastián, Basque Country, Spain
| | - Stuart Parkin
- NISE
Department, Max Planck Institute of Microstructure
Physics, 06120 Halle, Germany
| | - Kostya S. Novoselov
- Institute
for Functional Intelligent Materials, National
University of Singapore, 117544 Singapore
| | - Pengcheng Dai
- Department
of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Luis Balicas
- National
High Magnetic Field Laboratory, Florida
State University, Tallahassee, Florida 32310, United States
- Department
of Physics, Florida State University, Tallahassee, Florida 32306, United States
| | - Elton J. G. Santos
- Institute
for Condensed Matter Physics and Complex Systems, School of Physics
and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
- Donostia
International Physics Center (DIPC), 20018 Donostia-San Sebastián, Basque Country, Spain
- Higgs Centre
for Theoretical Physics, The University
of Edinburgh, Edinburgh EH9 3FD, United Kingdom
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35
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Shavit G, Oreg Y. Domain Formation Driven by the Entropy of Topological Edge Modes. PHYSICAL REVIEW LETTERS 2022; 128:156801. [PMID: 35499882 DOI: 10.1103/physrevlett.128.156801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 03/30/2022] [Indexed: 06/14/2023]
Abstract
In this Letter we study interacting systems with spontaneous discrete symmetry breaking, where the degenerate symmetry-broken states are topologically distinct gapped phases. Edge modes appear at domain walls between the two topological phases. In the presence of a weak disorder field conjugate to the order parameter, we find that the entropy of the edge modes drives a thermal transition between a gapped uniform phase and a phase with a disorder-induced domain structure. We characterize this transition using a phenomenological Landau functional, and corroborate our conclusions with a concrete microscopic model. Finally, we discuss the possibilities of experimental signatures of this phase transition, and propose graphene-based moiré heterostructures as candidate materials in which such a phase transition can be detected.
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Affiliation(s)
- Gal Shavit
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel, 76100
| | - Yuval Oreg
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel, 76100
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36
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Zhang Q, Zhang Y, Hou Y, Xu R, Jia L, Huang Z, Hao X, Zhou J, Zhang T, Liu L, Xu Y, Gao HJ, Wang Y. Nanoscale Control of One-Dimensional Confined States in Strongly Correlated Homojunctions. NANO LETTERS 2022; 22:1190-1197. [PMID: 35043640 DOI: 10.1021/acs.nanolett.1c04363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Construction of lateral junctions is essential to generate one-dimensional (1D) confined potentials that can effectively trap quasiparticles. A series of remarkable electronic phases in one dimension, such as Wigner crystallization, are expected to be realized in such junctions. Here, we demonstrate that we can precisely tune the 1D-confined potential with an in situ manipulation technique, thus providing a dynamic way to modify the correlated electronic states at the junctions. We confirm the existence of 1D-confined potential at the homojunction of two single-layer 1T-NbSe2 islands. Such potential is structurally sensitive and shows a nonmonotonic function of their interspacing. Moreover, there is a change of electronic properties from the correlated insulator to the generalized 1D Wigner crystallization while the confinement becomes strong. Our findings not only establish the capability to fabricate structures with dynamically tunable properties, but also pave the way toward more exotic correlated systems in low dimensions.
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Affiliation(s)
- Quanzhen Zhang
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Yu Zhang
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
- Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing 100081, China
| | - Yanhui Hou
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Runzhang Xu
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
| | - Liangguang Jia
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Zeping Huang
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Xiaoyu Hao
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Jiadong Zhou
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Teng Zhang
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Liwei Liu
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
| | - Yong Xu
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
| | - Hong-Jun Gao
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yeliang Wang
- School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
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37
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Cha P, Patel AA, Kim EA. Strange Metals from Melting Correlated Insulators in Twisted Bilayer Graphene. PHYSICAL REVIEW LETTERS 2021; 127:266601. [PMID: 35029498 DOI: 10.1103/physrevlett.127.266601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 09/24/2021] [Accepted: 11/01/2021] [Indexed: 06/14/2023]
Abstract
Even as the understanding of the mechanism behind correlated insulating states in magic-angle twisted bilayer graphene converges toward various kinds of spontaneous symmetry breaking, the metallic "normal state" above the insulating transition temperature remains mysterious, with its excessively high entropy and linear-in-temperature resistivity. In this Letter, we focus on the effects of fluctuations of the order parameters describing correlated insulating states at integer fillings of the low-energy flat bands on charge transport. Motivated by the observation of heterogeneity in the order-parameter landscape at zero magnetic field in certain samples, we conjecture the existence of frustrating extended-range interactions in an effective Ising model of the order parameters on a triangular lattice. The competition between short-distance ferromagnetic interactions and frustrating extended-range antiferromagnetic interactions leads to an emergent length scale that forms stripy mesoscale domains above the ordering transition. The gapless fluctuations of these heterogeneous configurations are found to be responsible for the linear-in-temperature resistivity as well as the enhanced low-temperature entropy. Our insights link experimentally observed linear-in-temperature resistivity and enhanced entropy to the strength of frustration or, equivalently, to the emergence of mesoscopic length scales characterizing order-parameter domains.
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Affiliation(s)
- Peter Cha
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - Aavishkar A Patel
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Eun-Ah Kim
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
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38
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Vallejo Bustamante J, Wu NJ, Fermon C, Pannetier-Lecoeur M, Wakamura T, Watanabe K, Taniguchi T, Pellegrin T, Bernard A, Daddinounou S, Bouchiat V, Guéron S, Ferrier M, Montambaux G, Bouchiat H. Detection of graphene's divergent orbital diamagnetism at the Dirac point. Science 2021; 374:1399-1402. [PMID: 34882473 DOI: 10.1126/science.abf9396] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- J Vallejo Bustamante
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - N J Wu
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France.,Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, Orsay, France
| | - C Fermon
- SPEC, CEA, CNRS, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
| | | | - T Wakamura
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France.,NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa, Japan
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Pellegrin
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - A Bernard
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - S Daddinounou
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - V Bouchiat
- Néel Institute, CNRS, 38000 Grenoble, France
| | - S Guéron
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - M Ferrier
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - G Montambaux
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - H Bouchiat
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
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39
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Xie M, MacDonald AH. Weak-Field Hall Resistivity and Spin-Valley Flavor Symmetry Breaking in Magic-Angle Twisted Bilayer Graphene. PHYSICAL REVIEW LETTERS 2021; 127:196401. [PMID: 34797159 DOI: 10.1103/physrevlett.127.196401] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 07/27/2021] [Accepted: 10/07/2021] [Indexed: 06/13/2023]
Abstract
Near a magic twist angle, the lowest energy conduction and valence bands of bilayer graphene moiré superlattices become extremely narrow. The band dispersion that remains is sensitive to the moiré's strain pattern, nonlocal tunneling between layers, and filling-factor-dependent Hartree and exchange band renormalizations. In this Letter, we analyze the influence of these band-structure details on the pattern of flavor symmetry breaking observed in this narrow band system and on the associated pattern of Fermi surface reconstructions revealed by weak-field Hall and Shubnikov-de Haas magnetotransport measurements.
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Affiliation(s)
- Ming Xie
- Physics Department, University of Texas at Austin, Austin, Texas 78712, USA
| | - A H MacDonald
- Physics Department, University of Texas at Austin, Austin, Texas 78712, USA
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40
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Geisenhof FR, Winterer F, Seiler AM, Lenz J, Xu T, Zhang F, Weitz RT. Quantum anomalous Hall octet driven by orbital magnetism in bilayer graphene. Nature 2021; 598:53-58. [PMID: 34616059 DOI: 10.1038/s41586-021-03849-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 07/22/2021] [Indexed: 11/09/2022]
Abstract
The quantum anomalous Hall (QAH) effect-a macroscopic manifestation of chiral band topology at zero magnetic field-has been experimentally realized only by the magnetic doping of topological insulators1-3 and the delicate design of moiré heterostructures4-8. However, the seemingly simple bilayer graphene without magnetic doping or moiré engineering has long been predicted to host competing ordered states with QAH effects9-11. Here we explore states in bilayer graphene with a conductance of 2 e2 h-1 (where e is the electronic charge and h is Planck's constant) that not only survive down to anomalously small magnetic fields and up to temperatures of five kelvin but also exhibit magnetic hysteresis. Together, the experimental signatures provide compelling evidence for orbital-magnetism-driven QAH behaviour that is tunable via electric and magnetic fields as well as carrier sign. The observed octet of QAH phases is distinct from previous observations owing to its peculiar ferrimagnetic and ferrielectric order that is characterized by quantized anomalous charge, spin, valley and spin-valley Hall behaviour9.
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Affiliation(s)
- Fabian R Geisenhof
- Physics of Nanosystems, Department of Physics, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Felix Winterer
- Physics of Nanosystems, Department of Physics, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Anna M Seiler
- Physics of Nanosystems, Department of Physics, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Jakob Lenz
- Physics of Nanosystems, Department of Physics, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Tianyi Xu
- Department of Physics, University of Texas at Dallas, Richardson, TX, USA
| | - Fan Zhang
- Department of Physics, University of Texas at Dallas, Richardson, TX, USA.
| | - R Thomas Weitz
- Physics of Nanosystems, Department of Physics, Ludwig-Maximilians-Universität München, Munich, Germany. .,Center for Nanoscience (CeNS), Munich, Germany. .,Munich Center for Quantum Science and Technology (MCQST), Munich, Germany. .,1st Physical Institute, Faculty of Physics, University of Göttingen, Göttingen, Germany.
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41
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He M, Zhang YH, Li Y, Fei Z, Watanabe K, Taniguchi T, Xu X, Yankowitz M. Competing correlated states and abundant orbital magnetism in twisted monolayer-bilayer graphene. Nat Commun 2021; 12:4727. [PMID: 34354061 PMCID: PMC8342414 DOI: 10.1038/s41467-021-25044-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 07/21/2021] [Indexed: 11/21/2022] Open
Abstract
Flat band moiré superlattices have recently emerged as unique platforms for investigating the interplay between strong electronic correlations, nontrivial band topology, and multiple isospin 'flavor' symmetries. Twisted monolayer-bilayer graphene (tMBG) is an especially rich system owing to its low crystal symmetry and the tunability of its bandwidth and topology with an external electric field. Here, we find that orbital magnetism is abundant within the correlated phase diagram of tMBG, giving rise to the anomalous Hall effect in correlated metallic states nearby most odd integer fillings of the flat conduction band, as well as correlated Chern insulator states stabilized in an external magnetic field. The behavior of the states at zero field appears to be inconsistent with simple spin and valley polarization for the specific range of twist angles we investigate, and instead may plausibly result from an intervalley coherent (IVC) state with an order parameter that breaks time reversal symmetry. The application of a magnetic field further tunes the competition between correlated states, in some cases driving first-order topological phase transitions. Our results underscore the rich interplay between closely competing correlated ground states in tMBG, with possible implications for probing exotic IVC ordering.
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Affiliation(s)
- Minhao He
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Ya-Hui Zhang
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Yuhao Li
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Zaiyao Fei
- Department of Physics, University of Washington, Seattle, WA, USA
| | - 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
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA.
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
| | - Matthew Yankowitz
- Department of Physics, University of Washington, Seattle, WA, USA.
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
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Low D, Ferguson GM, Jarjour A, Schaefer BT, Bachmann MD, Moll PJW, Nowack KC. Scanning SQUID microscopy in a cryogen-free dilution refrigerator. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:083704. [PMID: 34470407 DOI: 10.1063/5.0047652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 08/09/2021] [Indexed: 06/13/2023]
Abstract
We report a scanning superconducting quantum interference device (SQUID) microscope in a cryogen-free dilution refrigerator with a base temperature at the sample stage of at least 30 mK. The microscope is rigidly mounted to the mixing chamber plate to optimize thermal anchoring of the sample. The microscope housing fits into the bore of a superconducting vector magnet, and our design accommodates a large number of wires connecting the sample and sensor. Through a combination of vibration isolation in the cryostat and a rigid microscope housing, we achieve relative vibrations between the SQUID and the sample that allow us to image with micrometer resolution over a 150 µm range while the sample stage temperature remains at base temperature. To demonstrate the capabilities of our system, we show images acquired simultaneously of the static magnetic field, magnetic susceptibility, and magnetic fields produced by a current above a superconducting micrometer-scale device.
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Affiliation(s)
- D Low
- Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, New York 14853, USA
| | - G M Ferguson
- Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, New York 14853, USA
| | - Alexander Jarjour
- Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, New York 14853, USA
| | - Brian T Schaefer
- Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, New York 14853, USA
| | - Maja D Bachmann
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
| | - Philip J W Moll
- Laboratory of Quantum Materials (QMAT), Institute of Materials, École Polytechnique Fédéral de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Katja C Nowack
- Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, New York 14853, USA
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Tschirhart CL, Serlin M, Polshyn H, Shragai A, Xia Z, Zhu J, Zhang Y, Watanabe K, Taniguchi T, Huber ME, Young AF. Imaging orbital ferromagnetism in a moiré Chern insulator. Science 2021; 372:1323-1327. [PMID: 34045322 DOI: 10.1126/science.abd3190] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 05/13/2021] [Indexed: 12/23/2022]
Abstract
Electrons in moiré flat band systems can spontaneously break time-reversal symmetry, giving rise to a quantized anomalous Hall effect. In this study, we use a superconducting quantum interference device to image stray magnetic fields in twisted bilayer graphene aligned to hexagonal boron nitride. We find a magnetization of several Bohr magnetons per charge carrier, demonstrating that the magnetism is primarily orbital in nature. Our measurements reveal a large change in the magnetization as the chemical potential is swept across the quantum anomalous Hall gap, consistent with the expected contribution of chiral edge states to the magnetization of an orbital Chern insulator. Mapping the spatial evolution of field-driven magnetic reversal, we find a series of reproducible micrometer-scale domains pinned to structural disorder.
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Affiliation(s)
- C L Tschirhart
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
| | - M Serlin
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
| | - H Polshyn
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
| | - A Shragai
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
| | - Z Xia
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
| | - J Zhu
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
| | - Y Zhang
- Department of Physics, University of California, Santa Barbara, CA 93106, USA
| | - K Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - M E Huber
- Departments of Physics and Electrical Engineering, University of Colorado Denver, Denver, CO 80217, USA
| | - A F Young
- Department of Physics, University of California, Santa Barbara, CA 93106, USA.
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