1
|
Zhan F, Qin Z, Xu DH, Zhou X, Ma DS, Wang R. Design of Antiferromagnetic Second-Order Band Topology with Rotation Topological Invariants in Two Dimensions. NANO LETTERS 2024. [PMID: 38870320 DOI: 10.1021/acs.nanolett.4c01817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
The existence of fractionally quantized topological corner charge serves as a key indicator for two-dimensional (2D) second-order topological insulators (SOTIs), yet it has not been experimentally observed in realistic materials. Here, based on effective model analysis and symmetry arguments, we propose a strategy for achieving SOTI phases with in-gap corner states in 2D systems with antiferromagnetic (AFM) order. We discover that the band topology originates from the interplay between intrinsic spin-orbital coupling and interlayer AFM exchange interactions. Using first-principles calculations, we show that the 2D AFM SOTI phase can be realized in (MnBi2Te4)(Bi2Te3)m films. Moreover, we demonstrate that the SOTI states are linked to rotation topological invariants under 3-fold rotation symmetry C3, resulting in fractionally quantized corner charge, i.e., n 3 | e | (mod e). Due to the great achievements in (MnBi2Te4)(Bi2Te3)m systems, our results providing reliable material candidates for experimentally accessible AFM SOTIs should draw intense attention.
Collapse
Affiliation(s)
- Fangyang Zhan
- Institute for Structure and Function & Department of Physics & Chongqing Key Laboratory for Strongly Coupled Physics, Chongqing University, Chongqing 400044, People's Republic of China
| | - Zheng Qin
- Center of Quantum materials and devices, Chongqing University, Chongqing 400044, People's Republic of China
| | - Dong-Hui Xu
- Institute for Structure and Function & Department of Physics & Chongqing Key Laboratory for Strongly Coupled Physics, Chongqing University, Chongqing 400044, People's Republic of China
- Center of Quantum materials and devices, Chongqing University, Chongqing 400044, People's Republic of China
| | - Xiaoyuan Zhou
- Center of Quantum materials and devices, Chongqing University, Chongqing 400044, People's Republic of China
| | - Da-Shuai Ma
- Institute for Structure and Function & Department of Physics & Chongqing Key Laboratory for Strongly Coupled Physics, Chongqing University, Chongqing 400044, People's Republic of China
- Center of Quantum materials and devices, Chongqing University, Chongqing 400044, People's Republic of China
| | - Rui Wang
- Institute for Structure and Function & Department of Physics & Chongqing Key Laboratory for Strongly Coupled Physics, Chongqing University, Chongqing 400044, People's Republic of China
- Center of Quantum materials and devices, Chongqing University, Chongqing 400044, People's Republic of China
| |
Collapse
|
2
|
Bai Y, Zhang L, Mao N, Li R, Chen Z, Dai Y, Huang B, Niu C. Coupled Electronic and Magnonic Topological States in Two-Dimensional Ferromagnets. ACS NANO 2024; 18:13377-13383. [PMID: 38728267 DOI: 10.1021/acsnano.4c03529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2024]
Abstract
Magnetic materials offer a fertile playground for fundamental physics discovery, with not only electronic but also magnonic topological states intensively explored. However, one natural material with both electronic and magnonic nontrivial topologies is still unknown. Here, we demonstrate the coexistence of first-order topological magnon insulators (TMIs) and electronic second-order topological insulators (SOTIs) in 2D honeycomb ferromagnets, giving rise to the nontrivial corner states being connected by the charge-free magnonic edge states. We show that, with C 3 symmetry, the phase factor ± ϕ caused by the next nearest-neighbor Dzyaloshinskii-Moriya interaction breaks the pseudo-spin time-reversal symmetry T , which leads to the split of magnon bands, i.e., the emergence of TMIs with a nonzero Chern number of C = - 1 , in experimentally feasible candidates of MoI3, CrSiTe3, and CrGeTe3 monolayers. Moreover, protected by the C 3 symmetry, the electronic SOTIs characterized by nontrivial corner states are obtained, bridging the topological aspect of fermions and bosons with a high possibility of innovative applications in spintronics devices.
Collapse
Affiliation(s)
- Yingxi Bai
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Lichuan Zhang
- School of Physics and Electronic Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Ning Mao
- 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
| | - Zhiqi Chen
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - 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
| | - Chengwang Niu
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| |
Collapse
|
3
|
Li R, Zou X, Bai Y, Chen Z, Huang B, Dai Y, Niu C. Layer-coupled corner states in two-dimensional topological multiferroics. MATERIALS HORIZONS 2024; 11:2242-2247. [PMID: 38421336 DOI: 10.1039/d3mh01266b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
The structural diversity and controllability in two-dimensional (2D) materials offers an intriguing platform for exploring a wide range of topological phenomena. The layer degree of freedom, as a novel technique for material manipulation, requires further investigation regarding its association with topological states. Here, using first-principles calculations and a tight-binding model, we propose a novel mechanism that couples the second-order topological corner states with the layer degree of freedom. By analyzing the edge states, topological indices, and spectra of nanoflakes, we identify ferromagnetic H'-Co2XF2 (X = C, N) as 2D second-order topological insulators with intrinsic ferroelectricity. Moreover, the topological corner states strongly couple with the layer degree of freedom, and, remarkably, ferroelectricity provides a nonvolatile handle to manipulate the layer-polarized corner states. These findings open an avenue for the manipulation of second-order topological states and establish a bridge between ferroelectricity and nontrivial topology.
Collapse
Affiliation(s)
- Runhan Li
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China.
| | - Xiaorong Zou
- 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.
| | - Zhiqi Chen
- 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.
| | - Ying Dai
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China.
| | - Chengwang Niu
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China.
| |
Collapse
|
4
|
Yang YB, Wang JH, Li K, Xu Y. Higher-order topological phases in crystalline and non-crystalline systems: a review. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:283002. [PMID: 38574683 DOI: 10.1088/1361-648x/ad3abd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 04/04/2024] [Indexed: 04/06/2024]
Abstract
In recent years, higher-order topological phases have attracted great interest in various fields of physics. These phases have protected boundary states at lower-dimensional boundaries than the conventional first-order topological phases due to the higher-order bulk-boundary correspondence. In this review, we summarize current research progress on higher-order topological phases in both crystalline and non-crystalline systems. We firstly introduce prototypical models of higher-order topological phases in crystals and their topological characterizations. We then discuss effects of quenched disorder on higher-order topology and demonstrate disorder-induced higher-order topological insulators. We also review the theoretical studies on higher-order topological insulators in amorphous systems without any crystalline symmetry and higher-order topological phases in non-periodic lattices including quasicrystals, hyperbolic lattices, and fractals, which have no crystalline counterparts. We conclude the review by a summary of experimental realizations of higher-order topological phases and discussions on potential directions for future study.
Collapse
Affiliation(s)
- Yan-Bin Yang
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong Special Administrative Region of China, People's Republic of China
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
| | - Jiong-Hao Wang
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
| | - Kai Li
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
| | - Yong Xu
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
- Hefei National Laboratory, Hefei 230088, People's Republic of China
| |
Collapse
|
5
|
Chen M, Kong X, Xie X, Liu X, Li J, Peeters FM, Li L. Tunable valley polarization effect and second-order topological state in monolayer FeClSH. Phys Chem Chem Phys 2024; 26:3285-3295. [PMID: 38197170 DOI: 10.1039/d3cp05127g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
In two-dimensional (2D) materials, breaking the inversion symmetry plays an important role in valleytronics. Ferrovalley (FV) materials can achieve spontaneous valley polarization (VP) without additional modulation due to the magnetic exchange interaction and strong spin-orbit coupling. Using first-principles calculations, we predict a new 2D material, Janus FeClSH, which exhibits a large spontaneous VP. This monolayer is a perfect FV material, where the valence band maximum and conduction band minimum are located at the K/K' point. A large VP of 102.95 meV is spontaneously generated for the case of out-of-plane magnetization. Additionally, we propose that the irradiating circularly polarized light can be used to realize VP for the case of in-plane magnetization. Remarkably, a triangular nanoflake of FeClSH with armchair edges can show nontrivial corner states, exhibiting a second-order topological insulator (SOTI) state. The VP effect and SOTI state are tunable with the Hubbard U parameter, making the FeClSH monolayer promising for the study of the coupling between VP and SOTI.
Collapse
Affiliation(s)
- Mengteng Chen
- School of Science, Hebei University of Technology, Tianjin 300401, China.
| | - Xiangru Kong
- College of Sciences, Northeastern University, Shenyang 110819, China.
| | - Xiao Xie
- School of Science, Hebei University of Technology, Tianjin 300401, China.
| | - Xiaobiao Liu
- School of Science, Henan Agricultural University, Zhengzhou 450002, China
| | - Jia Li
- School of Science, Hebei University of Technology, Tianjin 300401, China.
| | - François M Peeters
- Centre for Quantum Metamaterials, HSE University, Moscow 101000, Russia
- Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, 60455-760 Fortaleza, Ceará, Brazil
| | - Linyang Li
- School of Science, Hebei University of Technology, Tianjin 300401, China.
| |
Collapse
|
6
|
Zhao W, Yang M, Xu R, Du X, Li Y, Zhai K, Peng C, Pei D, Gao H, Li Y, Xu L, Han J, Huang Y, Liu Z, Yao Y, Zhuang J, Du Y, Zhou J, Chen Y, Yang L. Topological electronic structure and spin texture of quasi-one-dimensional higher-order topological insulator Bi 4Br 4. Nat Commun 2023; 14:8089. [PMID: 38062024 PMCID: PMC10703900 DOI: 10.1038/s41467-023-43882-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 11/22/2023] [Indexed: 03/25/2024] Open
Abstract
The notion of topological insulators (TIs), characterized by an insulating bulk and conducting topological surface states, can be extended to higher-order topological insulators (HOTIs) hosting gapless modes localized at the boundaries of two or more dimensions lower than the insulating bulk. In this work, by performing high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements with submicron spatial and spin resolution, we systematically investigate the electronic structure and spin texture of quasi-one-dimensional (1D) HOTI candidate Bi4Br4. In contrast to the bulk-state-dominant spectra on the (001) surface, we observe gapped surface states on the (100) surface, whose dispersion and spin-polarization agree well with our ab-initio calculations. Moreover, we reveal in-gap states connecting the surface valence and conduction bands, which is a signature of the hinge states inside the (100) surface gap. Our findings provide compelling evidence for the HOTI phase of Bi4Br4. The identification of the higher-order topological phase promises applications based on 1D spin-momentum locked current in electronic and spintronic devices.
Collapse
Affiliation(s)
- Wenxuan Zhao
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Ming Yang
- School of Physics, Beihang University, Beijing, 100191, China
- Centre of Quantum and Matter Sciences, International Research Institute for Multidisciplinary Science, Beihang University, Beijing, 100191, China
| | - Runzhe Xu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Xian Du
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Yidian Li
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Kaiyi Zhai
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Cheng Peng
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK
| | - Ding Pei
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK
| | - Han Gao
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai, 201210, China
| | - Yiwei Li
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai, 201210, China
| | - Lixuan Xu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Junfeng Han
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
- Yangtze Delta Region Academy of Beijing Institute of Technology, Jiaxing, 314001, Zhejiang province, China
| | - Yuan Huang
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
- Yangtze Delta Region Academy of Beijing Institute of Technology, Jiaxing, 314001, Zhejiang province, China
| | - Zhongkai Liu
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai, 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai, 200031, China
| | - Yugui Yao
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China
- Yangtze Delta Region Academy of Beijing Institute of Technology, Jiaxing, 314001, Zhejiang province, China
| | - Jincheng Zhuang
- School of Physics, Beihang University, Beijing, 100191, China
- Centre of Quantum and Matter Sciences, International Research Institute for Multidisciplinary Science, Beihang University, Beijing, 100191, China
| | - Yi Du
- School of Physics, Beihang University, Beijing, 100191, China.
- Centre of Quantum and Matter Sciences, International Research Institute for Multidisciplinary Science, Beihang University, Beijing, 100191, China.
| | - Jinjian Zhou
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China.
| | - Yulin Chen
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK.
- School of Physical Science and Technology, ShanghaiTech University and CAS-Shanghai Science Research Center, Shanghai, 201210, China.
- ShanghaiTech Laboratory for Topological Physics, Shanghai, 200031, China.
| | - Lexian Yang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China.
- Frontier Science Center for Quantum Information, Beijing, 100084, China.
- Collaborative Innovation Center of Quantum Matter, Beijing, China.
| |
Collapse
|
7
|
Zhang X, Wang X, He T, Wang L, Yu WW, Liu Y, Liu G, Cheng Z. Magnetic topological materials in two-dimensional: theory, material realization and application prospects. Sci Bull (Beijing) 2023; 68:2639-2657. [PMID: 37734982 DOI: 10.1016/j.scib.2023.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 07/12/2023] [Accepted: 08/23/2023] [Indexed: 09/23/2023]
Abstract
Two-dimensional (2D) magnetism and nontrivial band topology are both areas of research that are currently receiving significant attention in the study of 2D materials. Recently, a novel class of materials has emerged, known as 2D magnetic topological materials, which elegantly combine 2D magnetism and nontrivial topology. This field has garnered increasing interest, especially due to the emergence of several novel magnetic topological states that have been generalized into the 2D scale. These states include antiferromagnetic topological insulators/semimetals, second-order topological insulators, and topological half-metals. Despite the rapid advancements in this emerging research field in recent years, there have been few comprehensive summaries of the state-of-the-art progress. Therefore, this review aims to provide a thorough analysis of current progress on 2D magnetic topological materials. We cover various 2D magnetic topological insulators, a range of 2D magnetic topological semimetals, and the novel 2D topological half-metals, systematically analyzing the basic topological theory, the course of development, the material realization, and potential applications. Finally, we discuss the challenges and prospects for 2D magnetic topological materials, highlighting the potential for future breakthroughs in this exciting field.
Collapse
Affiliation(s)
- Xiaoming Zhang
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, and School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China
| | - Xiaotian Wang
- School of Physical Science and Technology, Southwest University, Chongqing 400715, China
| | - Tingli He
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, and School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China
| | - Lirong Wang
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, and School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China
| | - Wei-Wang Yu
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, and School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China
| | - Ying Liu
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, and School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China
| | - Guodong Liu
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, and School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China.
| | - Zhenxiang Cheng
- Institute for Superconducting and Electronic Materials (ISEM), University of Wollongong, Wollongong 2500, Australia.
| |
Collapse
|
8
|
Kukreti S, Ramawat S, Singh N, Dixit A. Strain-engineered thermophysical properties ranging from band-insulating to topological insulating phases in β-antimonene. NANOSCALE 2023; 15:13997-14006. [PMID: 37455636 DOI: 10.1039/d3nr02255b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
The use of strain in semiconductors allows extensive modification of their properties. Due to their robust mechanical strength and flexibility, atomically thin 2D materials are very well suited for strain engineering to extract exotic electronic and thermophysical properties. We investigated the structural, electronic, thermal, and vibrational characteristics along with the phonon and carrier dynamics of β-Sb elemental monolayers for achieving the band-insulating phase at no strain and topological insulating phase at ∼15% biaxial strain. A reduction in stiffness was noticed due to the weakening of the π and σ bonds with strain, leading to anharmonicity in the system. This was further reflected by the drop in lattice thermal conductivity (κl) from 4.5 to 3.1 W m-1 K-1 at 15% strain, i.e., in the topological phase. The appearance of helical edge states at 15% strain and meeting the Z2 invariant criterion confirm the non-trivial topological state. The significant contribution of the out-of-plane A1g vibrational mode was noticed in the topological phase compared with the band-insulating phase. Further, the observed larger reduction in hole lifetime could be attributed to strong scattering near the valence band edge. Importantly, the dominance of the out-of-plane optical modes contributes significantly along the band edges to the topological phase, which is primarily due to the reduced buckling height under strain. Thus, this work emphasizes the microscopic origin of the onset of the topological phase in strained β-Sb monolayers and provides strain-engineered structure-property correlations for better insights.
Collapse
Affiliation(s)
- Sumit Kukreti
- Advanced Materials and Device (A-MAD) Laboratory, Department of Physics, Indian Institute of Technology Jodhpur, 342030, India.
| | - Surbhi Ramawat
- Advanced Materials and Device (A-MAD) Laboratory, Department of Physics, Indian Institute of Technology Jodhpur, 342030, India.
| | - Nirpendra Singh
- Department of Physics, Khalifa University of Science and Technology, Abu Dhabi-127788, United Arab Emirates
| | - Ambesh Dixit
- Advanced Materials and Device (A-MAD) Laboratory, Department of Physics, Indian Institute of Technology Jodhpur, 342030, India.
| |
Collapse
|
9
|
Zhu WQ, Shan WY. Theoretical studies of magneto-optical Kerr and Faraday effects in two-dimensional second-order topological insulators. Sci Rep 2023; 13:12599. [PMID: 37537224 PMCID: PMC10400575 DOI: 10.1038/s41598-023-39644-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 07/28/2023] [Indexed: 08/05/2023] Open
Abstract
Optical approaches are useful for studying the electronic and spin structure of materials. Here, based on the tight-binding model and linear response theory, we investigate the magneto-optical Kerr and Faraday effects in two-dimensional second-order topological insulators (SOTI) with external magnetization. We find that orbital-dependent Zeeman term induces band crossings for SOTI phase, which are absent for trivial phase. In the weak-magnetization regime, these crossings give rise to giant jumps (peaks) of Kerr and Faraday angles (ellipticity) for SOTI phase. In the strong-magnetization regime, we find that two nearly flat bands are formed at the high-symmetry point of Brillouin zone of SOTI phase. These flat bands give rise to two successive giant jumps (peaks) of Kerr and Faraday angles (ellipticity). These phenomena provide new possibilities to characterize and detect the two-dimensional SOTI phase.
Collapse
Affiliation(s)
- Wan-Qing Zhu
- Department of Physics, School of Physics and Materials Science, Guangzhou University, Guangzhou, 510006, China
| | - Wen-Yu Shan
- Department of Physics, School of Physics and Materials Science, Guangzhou University, Guangzhou, 510006, China.
| |
Collapse
|
10
|
Bai Y, Mao N, Li R, Dai Y, Huang B, Niu C. Engineering Second-Order Corner States in 2D Multiferroics. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2206574. [PMID: 36642812 DOI: 10.1002/smll.202206574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/18/2022] [Indexed: 06/17/2023]
Abstract
The understanding and manipulate of the second-order corner states are central to both fundamental physics and future topotronics applications. Despite the fact that numerous second-order topological insulators (SOTIs) are achieved, the efficient engineering in a given material remains elusive. Here, the emergence of 2D multiferroics SOTIs in SbAs and BP5 monolayers is theoretically demonstrated, and an efficient and straightforward way for engineering the nontrivial corner states by ferroelasticity and ferroelectricity is remarkably proposed. With ferroelectric polarization of SbAs and BP5 monolayers, the nontrivial corner states emerge in the mirror symmetric corners and are perpendicular to orientations of the in-plane spontaneous polarization. And remarkably the spatial distribution of the corner states can be effectively tuned by a ferroelastic switching. At the intermediate states of both ferroelectric and ferroelastic switchings, the corner states disappear. These finding not only combines exotic SOTIs with multiferroics but also pave the way for experimental discovery of 2D tunable SOTIs.
Collapse
Affiliation(s)
- 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
| | - Runhan Li
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100, China
| | - 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
| | - Chengwang Niu
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100, China
| |
Collapse
|
11
|
Kats VN, Shelukhin LA, Usachev PA, Averyanov DV, Karateev IA, Parfenov OE, Taldenkov AN, Tokmachev AM, Storchak VG, Pavlov VV. Femtosecond optical orientation triggering magnetization precession in epitaxial EuO films. NANOSCALE 2023; 15:2828-2836. [PMID: 36688382 DOI: 10.1039/d2nr04872h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Light-induced magnetization response unfolding on a temporal scale down to femtoseconds presents a way to convey information via spin manipulation. The advancement of the field requires exploration of new materials implementing various mechanisms for ultrafast magnetization dynamics. Here, pump-probe measurements of EuO-based ferromagnets by a time-resolved two-colour stroboscopic technique are reported. Epitaxial films of the pristine semiconductor and metallic Gd-doped EuO demonstrate photo-induced magnetization precession. Comparative experimental studies of both systems are carried out varying temperature, magnetic field, and polarization light helicity of the pump beam, followed by numerical estimates. The study establishes optical spin orientation by the electronic transition 4f75d0 → 4f65d1 as a mechanism triggering collective magnetization precession in these materials. The results suggest applications of EuO-based systems in optoelectronics and spintronics.
Collapse
Affiliation(s)
| | | | | | - Dmitry V Averyanov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Igor A Karateev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Oleg E Parfenov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Alexander N Taldenkov
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Andrey M Tokmachev
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | - Vyacheslav G Storchak
- National Research Center "Kurchatov Institute", Kurchatov Sq. 1, Moscow 123182, Russia.
| | | |
Collapse
|
12
|
Li R, Mao N, Wu X, Huang B, Dai Y, Niu C. Robust Second-Order Topological Insulators with Giant Valley Polarization in Two-Dimensional Honeycomb Ferromagnets. NANO LETTERS 2023; 23:91-97. [PMID: 36326600 DOI: 10.1021/acs.nanolett.2c03680] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Magnetic topological states have attracted great attention that provide exciting platforms for exploring prominent physical phenomena and applications of topological spintronics. Here, using a tight-binding model and first-principles calculations, we put forward that, in contrast to previously reported magnetic second-order topological insulators (SOTIs), robust SOTIs can emerge in two-dimensional ferromagnets regardless of magnetization directions. Remarkably, we identify intrinsic ferromagnetic 2H-RuCl2 and Janus VSSe monolayers as experimentally feasible candidates of predicted robust SOTIs with the emergence of nontrivial corner states along different magnetization directions. Moreover, under out-of-plane magnetization, we unexpectedly point out that the valley polarization of SOTIs can be huge and much larger than that of the known ferrovalley materials, opening up a technological avenue to bridge the valleytronics and higher-order topology with high possibility of innovative applications in topological spintronics and valleytronics.
Collapse
Affiliation(s)
- Runhan Li
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan250100, China
| | - Ning Mao
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan250100, China
| | - Xinming Wu
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan250100, China
| | - Baibiao Huang
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan250100, China
| | - Ying Dai
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan250100, China
| | - Chengwang Niu
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan250100, China
| |
Collapse
|
13
|
Hu T, Zhang T, Mu H, Wang Z. Intrinsic Second-Order Topological Insulator in Two-Dimensional Covalent Organic Frameworks. J Phys Chem Lett 2022; 13:10905-10911. [PMID: 36394555 DOI: 10.1021/acs.jpclett.2c02683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
As an intriguing topological phase, higher-order topological insulators have attracted tremendous attention, but the candidate materials are limited in artificial and inorganic systems. In this work, we propose a universal approach to search for two-dimensional (2D) second-order topological insulators (SOTIs) in covalent organic frameworks (COFs) with C3 symmetric cores. The underlying mechanism is illustrated through tight-binding calculations in a star lattice, showing the 2D SOTI in an overlooked energy window between two Kagome-bands with four types of nontrivial band structures. The emergence of the unique topological edge and corner states can be understood from the Su-Schrieffer-Heeger model. Furthermore, using the frontier orbital of the monomer building block as an indicator, the 2D SOTI is directly confirmed in three realistic COFs by first-principles calculations. Our results not only extend the concept of organic topological insulators from first-order to second-order but also demonstrate the universal existence of intrinsic higher-order topology in 2D COFs.
Collapse
Affiliation(s)
- Tianyi Hu
- Hefei National Research Center for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui230026, China
| | - Tingfeng Zhang
- Hefei National Research Center for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui230026, China
| | - Haimen Mu
- Hefei National Research Center for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui230026, China
| | - Zhengfei Wang
- Hefei National Research Center for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui230088, China
| |
Collapse
|
14
|
Mao N, Li R, Dai Y, Huang B, Yan B, Niu C. Orbital Shift-Induced Boundary Obstructed Topological Materials with a Large Energy Gap. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2202564. [PMID: 35905489 PMCID: PMC9507389 DOI: 10.1002/advs.202202564] [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: 05/03/2022] [Revised: 06/08/2022] [Indexed: 06/15/2023]
Abstract
Boundary obstructed topological phases caused by Wannier orbital shift between ordinary atomic sites are proposed, which, however, cannot be indicated by symmetry eigenvalues at high symmetry momenta (symmetry indicators) in bulk. On the open boundary, Wannier charge centers can shift to different atoms from those in bulk, leading to in-gap surface states, higher-order hinge states or corner states. To demonstrate such orbital shift-induced boundary obstructed topological insulators, eight material candidates are predicted, all of which are overlooked in the present topological databases. Metallic surface states, hinge states, or corner states cover the large bulk energy gap (e.g., more than 1 eV in TlGaTe2 ) at related boundary, which are ready for experimental detection. Additionally, these materials are also fragile topological insulators with hourglass-like surface states.
Collapse
Affiliation(s)
- Ning Mao
- School of PhysicsState Key Laboratory of Crystal MaterialsShandong UniversityJinan250100China
| | - Runhan Li
- School of PhysicsState Key Laboratory of Crystal MaterialsShandong UniversityJinan250100China
| | - Ying Dai
- School of PhysicsState Key Laboratory of Crystal MaterialsShandong UniversityJinan250100China
| | - Baibiao Huang
- School of PhysicsState Key Laboratory of Crystal MaterialsShandong UniversityJinan250100China
| | - Binghai Yan
- Department of Condensed Matter PhysicsWeizmann Institute of ScienceRehovotIsrael
| | - Chengwang Niu
- School of PhysicsState Key Laboratory of Crystal MaterialsShandong UniversityJinan250100China
| |
Collapse
|
15
|
Wang C, Liu F, Huang H. Effective Model for Fractional Topological Corner Modes in Quasicrystals. PHYSICAL REVIEW LETTERS 2022; 129:056403. [PMID: 35960584 DOI: 10.1103/physrevlett.129.056403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 07/06/2022] [Indexed: 06/15/2023]
Abstract
High-order topological insulators (HOTIs), as generalized from topological crystalline insulators, are characterized with lower-dimensional metallic boundary states protected by spatial symmetries of a crystal, whose theoretical framework based on band inversion at special k points cannot be readily extended to quasicrystals because quasicrystals contain rotational symmetries that are not compatible with crystals, and momentum is no longer a good quantum number. Here, we develop a low-energy effective model underlying HOTI states in 2D quasicrystals for all possible rotational symmetries. By implementing a novel Fourier transform developed recently for quasicrystals and approximating the long-wavelength behavior by their large-scale average, we construct an effective k·p Hamiltonian to capture the band inversion at the center of a pseudo-Brillouin zone. We show that an in-plane Zeeman field can induce mass kinks at the intersection of adjacent edges of a 2D quasicrystal topological insulators and generate corner modes (CMs) with fractional charge, protected by rotational symmetries. Our model predictions are confirmed by numerical tight-binding calculations. Furthermore, when the quasicrystal is proximitized by an s-wave superconductor, Majorana CMs can also be created by tuning the field strength and chemical potential. Our work affords a generic approach to studying the low-energy physics of quasicrystals, in association with topological excitations and fractional statistics.
Collapse
Affiliation(s)
- Citian Wang
- School of Physics, Peking University, Beijing 100871, China
| | - Feng Liu
- Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA
| | - Huaqing Huang
- School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- Center for High Energy Physics, Peking University, Beijing 100871, China
| |
Collapse
|
16
|
Lei Y, Luo XW, Zhang S. Second-order topological insulator in periodically driven optical lattices. OPTICS EXPRESS 2022; 30:24048-24061. [PMID: 36225074 DOI: 10.1364/oe.457757] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 06/06/2022] [Indexed: 06/16/2023]
Abstract
The higher-order topological insulator (HOTI) is a new type of topological system which has special bulk-edge correspondence compared with conventional topological insulators. In this work, we propose a scheme to realize Floquet HOTI with ultracold atoms in optical lattices. With the combination of periodically spin-dependent driving of the superlattices and a long-range coupling term, a Floquet second-order topological insulator with four zero-energy corner states emerges, whose Wannier bands are gapless and exhibit interesting bulk topology. Furthermore, the nearest-neighbor anisotropic coupling term also induced other intriguing topological phenomena, e.g. non-topologically protected corner states and topological semimetal for two different types of lattice structures respectively. Our scheme may give insight into the construction of different types of higher-order topological insulators in synthetic systems. It also provides an experimentally feasible platform to research the relations between different types of topological states and may have a wide range of applications in future.
Collapse
|
17
|
Mu H, Liu B, Hu T, Wang Z. Kekulé Lattice in Graphdiyne: Coexistence of Phononic and Electronic Second-Order Topological Insulator. NANO LETTERS 2022; 22:1122-1128. [PMID: 35044189 DOI: 10.1021/acs.nanolett.1c04239] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Topological physics has been extensively studied in different kinds of bosonic and Fermionic systems, but the coexistence of topological phonons and electrons in one single material has seldom been reported. Recently, graphdiyne has been proposed as a two-dimensional (2D) electronic second-order topological insulator (SOTI). In this work, we found that graphdiyne is equivalent to Kekulé lattice, also realizing a 2D phononic SOTI in both out-of-plane and in-plane modes. Depending on edge terminations, the characterized topological corner states can be either inside or outside the bulk gap and are tunable by the local corner potential. Most remarkably, a unique selectivity of space and symmetry is revealed in the electron-phonon coupling between the localized phononic and electronic topological corner states. Our results not only demonstrate the phononic higher-order band topology in a real carbon material but also provide an opportunity to investigate the interplay between phononic and electronic higher-order topological states.
Collapse
Affiliation(s)
- Haimen Mu
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Bing Liu
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Tianyi Hu
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Zhengfei Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| |
Collapse
|
18
|
Chen C, Zeng XT, Chen Z, Zhao YX, Sheng XL, Yang SA. Second-Order Real Nodal-Line Semimetal in Three-Dimensional Graphdiyne. PHYSICAL REVIEW LETTERS 2022; 128:026405. [PMID: 35089745 DOI: 10.1103/physrevlett.128.026405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 11/11/2021] [Accepted: 12/21/2021] [Indexed: 06/14/2023]
Abstract
Real topological phases featuring real Chern numbers and second-order boundary modes have been a focus of current research, but finding their material realization remains a challenge. Here, based on first-principles calculations and theoretical analysis, we reveal the already experimentally synthesized three-dimensional (3D) graphdiyne as the first realistic example of the recently proposed second-order real nodal-line semimetal. We show that the material hosts a pair of real nodal rings, each protected by two topological charges: a real Chern number and a 1D winding number. The two charges generate distinct topological boundary modes at distinct boundaries. The real Chern number leads to a pair of hinge Fermi arcs, whereas the winding number protects a double drumhead surface bands. We develop a low-energy model for 3D graphdiyne which captures the essential topological physics. Experimental aspects and possible topological transition to a 3D real Chern insulator phase are discussed.
Collapse
Affiliation(s)
- Cong Chen
- School of Physics, Beihang University, Beijing 100191, China
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore 487372, Singapore
| | - Xu-Tao Zeng
- School of Physics, Beihang University, Beijing 100191, China
| | - Ziyu Chen
- School of Physics, Beihang University, Beijing 100191, China
| | - Y X Zhao
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Xian-Lei Sheng
- School of Physics, Beihang University, Beijing 100191, China
| | - Shengyuan A Yang
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore 487372, Singapore
| |
Collapse
|
19
|
Guo J, Sun J, Zhu X, Li CA, Guo H, Feng S. Quantum Monte Carlo study of topological phases on a spin analogue of Benalcazar-Bernevig-Hughes model. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:035603. [PMID: 34663768 DOI: 10.1088/1361-648x/ac30b4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 10/18/2021] [Indexed: 06/13/2023]
Abstract
We study the higher-order topological spin phases based on a spin analogue of Benalcazar-Bernevig-Hughes model in two dimensions using large-scale quantum Monte Carlo simulations. A continuous Néel-valence bond solid quantum phase transition is revealed by tuning the ratio between dimerized spin couplings, namely, the weak and strong exchange couplings. Through the finite-size scaling analysis, we identify the phase critical points, and consequently, map out the full phase diagrams in related parameter spaces. Particularly, we find that the valence bond solid phase can be a higher-order topological spin phase, which has a gap for spin excitations in the bulk while demonstrates characteristic gapless spin modes at corners of open lattices. We further discuss the connection between the higher-order topological spin phases and the electronic correlated higher-order phases, and find both of them possess gapless spin corner modes that are protected by higher-order topology. Our result exemplifies higher-order physics in the correlated spin systems and will contribute to further understandings of the many-body higher-order topological phenomena.
Collapse
Affiliation(s)
- Jiaojiao Guo
- Department of Physics, Beihang University, Beijing, 100191, People's Republic of China
| | - Junsong Sun
- Department of Physics, Beihang University, Beijing, 100191, People's Republic of China
| | - Xingchuan Zhu
- Center for Basic Teaching and Experiment, Nanjing University of Science and Technology, Jiangyin 214443, People's Republic of China
| | - Chang-An Li
- Institute for Theoretical Physics and Astrophysics, University of Würzburg, D-97074 Würzburg, Germany
| | - Huaiming Guo
- Department of Physics, Beihang University, Beijing, 100191, People's Republic of China
| | - Shiping Feng
- Department of Physics, Beijing Normal University, Beijing, 100875, People's Republic of China
| |
Collapse
|
20
|
Huang X, Lu J, Yan Z, Yan M, Deng W, Chen G, Liu Z. Acoustic higher-order topology derived from first-order with built-in Zeeman-like fields. Sci Bull (Beijing) 2021; 67:488-494. [DOI: 10.1016/j.scib.2021.11.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/20/2021] [Accepted: 11/23/2021] [Indexed: 10/19/2022]
|
21
|
Higher-order topological insulator in cubic semiconductor quantum wells. Sci Rep 2021; 11:21060. [PMID: 34702881 PMCID: PMC8548307 DOI: 10.1038/s41598-021-00577-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Accepted: 10/07/2021] [Indexed: 11/30/2022] Open
Abstract
The search for exotic new topological states of matter in widely accessible materials, for which the manufacturing process is mastered, is one of the major challenges of the current topological physics. Here we predict higher order topological insulator state in quantum wells based on the most common semiconducting materials. By successively deriving the bulk and boundary Hamiltonians, we theoretically prove the existence of topological corner states due to cubic symmetry in quantum wells with double band inversion. We show that the appearance of corner states does not depend solely on the crystallographic orientation of the meeting edges, but also on the growth orientation of the quantum well. Our theoretical results significantly extend the application potential of topological quantum wells based on IV, II–VI and III–V semiconductors with diamond or zinc-blende structures.
Collapse
|
22
|
Higher-order topological Mott insulator on the pyrochlore lattice. Sci Rep 2021; 11:20270. [PMID: 34642375 PMCID: PMC8511174 DOI: 10.1038/s41598-021-99213-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 09/14/2021] [Indexed: 11/09/2022] Open
Abstract
We provide the first unbiased evidence for a higher-order topological Mott insulator in three dimensions by numerically exact quantum Monte Carlo simulations. This insulating phase is adiabatically connected to a third-order topological insulator in the noninteracting limit, which features gapless modes around the corners of the pyrochlore lattice and is characterized by a [Formula: see text] spin-Berry phase. The difference between the correlated and non-correlated topological phases is that in the former phase the gapless corner modes emerge only in spin excitations being Mott-like. We also show that the topological phase transition from the third-order topological Mott insulator to the usual Mott insulator occurs when the bulk spin gap solely closes.
Collapse
|
23
|
Zhuo W, Lei B, Wu S, Yu F, Zhu C, Cui J, Sun Z, Ma D, Shi M, Wang H, Wang W, Wu T, Ying J, Wu S, Wang Z, Chen X. Manipulating Ferromagnetism in Few-Layered Cr 2 Ge 2 Te 6. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2008586. [PMID: 34173269 DOI: 10.1002/adma.202008586] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 04/18/2021] [Indexed: 06/13/2023]
Abstract
The discovery of magnetism in 2D materials offers new opportunities for exploring novel quantum states and developing spintronic devices. In this work, using field-effect transistors with solid ion conductors as the gate dielectric (SIC-FETs), we have observed a significant enhancement of ferromagnetism associated with magnetic easy-axis switching in few-layered Cr2 Ge2 Te6 . The easy axis of the magnetization, inferred from the anisotropic magnetoresistance, can be uniformly tuned from the out-of-plane direction to an in-plane direction by electric field in the few-layered Cr2 Ge2 Te6 . Additionally, the Curie temperature, obtained from both the Hall resistance and magnetoresistance measurements, increases from 65 to 180 K in the few-layered sample by electric gating. Moreover, the surface of the sample is fully exposed in the SIC-FET device configuration, making further heterostructure-engineering possible. This work offers an excellent platform for realizing electrically controlled quantum phenomena in a single device.
Collapse
Affiliation(s)
- Weizhuang Zhuo
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Bin Lei
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Shuang Wu
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), and Department of physics, Fudan University, Shanghai, 200433, China
| | - Fanghang Yu
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Changsheng Zhu
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Jianhua Cui
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Zeliang Sun
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Donghui Ma
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Mengzhu Shi
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Honghui Wang
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Wenxiang Wang
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Tao Wu
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Jianjun Ying
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Shiwei Wu
- State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), and Department of physics, Fudan University, Shanghai, 200433, China
- Shanghai Research Center for Quantum Sciences, Shanghai, 201315, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Zhenyu Wang
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Xianhui Chen
- Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, and Key Laboratory of Strongly-Couple Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- CAS Center for Excellence in Quantum Information and Quantum Physics, Hefei, Anhui, 230026, China
| |
Collapse
|
24
|
Wang JH, Yang YB, Dai N, Xu Y. Structural-Disorder-Induced Second-Order Topological Insulators in Three Dimensions. PHYSICAL REVIEW LETTERS 2021; 126:206404. [PMID: 34110216 DOI: 10.1103/physrevlett.126.206404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 04/22/2021] [Indexed: 06/12/2023]
Abstract
Higher-order topological insulators are established as topological crystalline insulators protected by crystalline symmetries. One celebrated example is the second-order topological insulator in three dimensions that hosts chiral hinge modes protected by crystalline symmetries. Since amorphous solids are ubiquitous, it is important to ask whether such a second-order topological insulator can exist in an amorphous system without any spatial order. Here, we predict the existence of a second-order topological insulating phase in an amorphous system without any crystalline symmetry. Such a topological phase manifests in the winding number of the quadrupole moment, the quantized longitudinal conductance, and the hinge states. Furthermore, in stark contrast to the viewpoint that structural disorder should be detrimental to the higher-order topological phase, we remarkably find that structural disorder can induce a second-order topological insulator from a topologically trivial phase in a regular geometry. We finally demonstrate the existence of a second-order topological phase in amorphous systems with time-reversal symmetry.
Collapse
Affiliation(s)
- Jiong-Hao Wang
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
| | - Yan-Bin Yang
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
| | - Ning Dai
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
| | - Yong Xu
- Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, People's Republic of China
- Shanghai Qi Zhi Institute, Shanghai 200030, People's Republic of China
| |
Collapse
|