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Large Band Gap Quantum Anomalous Hall Phase in Hexagonal Organometallic Frameworks

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arXiv 2018年

作者： Jin, Yuanjun Chen, Zhongjia Xia, Bowen Zhao, Yujun Wang, Rui Xu, Hu Department of Physics & Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Department of Physics South China University of Technology Guangzhou510640 China Institute for Structure and Function Department of physics Chongqing University Chongqing400044 China

The nontrivial band gap plays a critical role in quantum anomalous Hall (QAH) insulators. In this work, we propose that the intrinsic QAH phase with sizable band gaps up to 367 meV is achieved in two-dimensional hexagonal organometallic frameworks (HOMFs). Based on first-principles calculations and effective model analysis, we uncover that these large band gaps in transition metal based HOMFs are opened by strong spin-orbital coupling of the localized 4d or 5d electrons. Importantly, we reveal that Coulomb correlations can further significantly enhance the nontrivial band gaps. In addition, we suggest a possible avenue to grow these organometallic QAH insulators on a semiconducting SiC(111) substrate, and the topological features are perfectly preserved due to the van der Waals interaction. Our work shows that the correlation remarkably enhances the nontrivial band gaps, providing exotic candidates to realize the QAH states at high temperatures. Copyright © 2018, The Authors. All rights reserved.

关键词： Energy gap

Ideal Intersecting Nodal Ring Phonons in a Body-Centered Cubic C8

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arXiv 2018年

作者： Jin, Y.J. Chen, Z.J. Xia, B.W. Zhao, Y.J. Wang, R. Xu, H. Department of Physics & Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Department of Physics South China University of Technology Guangzhou510640 China Institute for Structure and Function & Department of physics Chongqing University Chongqing400044 China

Carbon, a basic versatile element in our universe, exhibits rich varieties of allotropic phases, most of which possess promising nontrivial topological fermions. In this work, we identify a distinct topological phonon phase in a realistic carbon allotrope with a body-centered cubic structure, termed bcc-C8. We show by symmetry arguments and effective model analysis that there are three intersecting phonon nodal rings perpendicular to each other in different planes. The intersecting phonon nodal rings are protected by time-reversal and inversion symmetries, which quantize the corresponding Berry phase into integer multiples of π. Unlike the electron systems, the phonon nodal rings in bcc-C8 are guaranteed to remain gapless due to the lack of spin-orbital coupling. The nearly flat drumhead surface states projected on semi-infinite (001) and (110) surfaces of bcc-C8 are clearly visible. Our findings not only discover promising nodal ring phonons in a carbon allotrope, but also provide emergent avenues for exploring topological phonons beyond fermionic electrons in carbon-allotropic structures with attractive features. Copyright © 2018, The Authors. All rights reserved.

关键词： Phonons

From atomic semimetal to topological nontrivial insulator

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Physical Review B 2022年第16期105卷 165135-165135页

作者： Xiao-Ping Li Da-Shuai Ma Cheng-Cheng Liu Zhi-Ming Yu 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 Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China Chongqing Key Laboratory for Strongly Coupled Physics and Institute for Structure and Function Department of Physics Chongqing University Chongqing 401331 China

Topological band insulators and (semi-)metals can arise out of atomic insulators when the hopping strength between electrons increases. Such topological phases are separated from the atomic insulator by a bulk gap closing. In this paper, we show that in many (magnetic) space groups, the crystals with certain Wyckoff positions and atomic orbitals being occupied must be semimetals in the atomic limit, e.g., the hopping strength between electrons is infinitesimal but not vanishing, which then are termed atomic semimetals (ASMs). We derive a sufficient condition for realizing ASMs in both spinless and spinful systems. Remarkably, with both symmetries and electron fillings of system preserved, increasing the hopping strength between electrons may transform an ASM into an insulator, and the induced insulators inevitably are topologically nontrivial. Particularly, using silicon as an example, we show the ASM criterion can discover the obstructed atomic insulators (OAIs) that are marked as trivial insulators on the topological quantum chemistry website. Our paper not only establishes an efficient way to identify and design topologically nontrivial insulators, but also predicts that the group-IV elemental semiconductors are ideal candidate materials for OAI.

关键词： Electronic structure Surface states Topological materials

Robustness of Half-Integer Quantized Hall Conductivity against Disorder in an Anisotropic Dirac Semimetal with Parity Anomaly

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arXiv 2023年

作者： Ning, Zhen Ding, Xianyong Xu, Dong-Hui Wang, Rui Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Center of Quantum Materials and Devices Chongqing University Chongqing400044 China

Two-dimensional Dirac semimetals with a single massless Dirac cone exhibit the parity anomaly. Usually, such a kind of anomalous topological semimetallic phase in real materials is unstable where any amount of disorder can drive it into a diffusive metal and destroy the half-integer quantized Hall conductivity as an indicator of parity anomaly. Here, based on low-energy effective model, we propose an anisotropic Dirac semimetal which explicitly breaks time-reversal symmetry and carries a half-integer quantized Hall conductivity. This topological semimetallic phase can be realized on a deformed honeycomb lattice subjected to a magnetic flux. Moreover, we perceptively investigate the disorder correction to the Hall conductivity. The results show that the effects of disorder can be strongly suppressed and thereby the nearly half-integer quantization of Hall conductivity can exist in a wide region of disorder, indicating that our proposed anisotropic Dirac semimetal is an exciting platform to investigate the parity anomaly phenomena. Copyright © 2023, The Authors. All rights reserved.

关键词： Topology

Controllable Weyl Nodes and Fermi Arcs from Floquet Engineering Triple Fermions

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arXiv 2024年

作者： Huang, Shengpu Zhan, Fangyang Ding, Xianyong Xu, Dong-Hui Ma, Da-Shuai Wang, Rui Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Center of Quantum Materials and Devices Chongqing University Chongqing400044 China

Floquet engineering with periodic driving as a powerful tool for designing desirable topological states has been the subject of intense recent studies. Here, we present the application of Floquet engineering to investigate evolution of topological triple fermions under irradiation of circularly polarized light (CPL), a phenomenon that currently remains a mystery. By using first-principles calculations and Floquet theorem, we demonstrate that WC-type TiO and its analogues are promising candidates for Floquet engineering of triple fermions. The symmetry analysis reveals that the electric field of CPL can break the specific symmetries, such as the time-reversal symmetry and its combination of spatial symmetries, inducing a transition to a flexibly controllable Weyl semimetallic phase. The survived spatial symmetry, controlled by light, guarantees that the Weyl nodes are located along the high-symmetry line or in high-symmetry planes in momentum space. Our findings focusing on Floquet engineering in realistic materials featured by triple fermions would facilitate both theoretical and experimental interest. © 2024, CC BY.

关键词： Topology

Circularly polarized light irradiated ferromagnetic MnBi2Te4: the long-sought ideal Weyl semimetal

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arXiv 2024年

作者： Fan, Shuai Huang, Shengpu Chen, Zhuo Zhan, Fangyang Ding, Xian-Yong Ma, Da-Shuai Wang, Rui Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Center of Quantum Materials and Devices Chongqing University Chongqing400044 China

The interaction between light and non-trivial energy band topology allows for the precise manipulation of topological quantum states, which has attracted intensive interest in condensed matter physics. In this work, using first-principles calculations, we studied the topological transition of ferromagnetic (FM) MnBi2Te4 upon irradiation with circularly polarized light (CPL). We revealed that the MnBi2Te4 can be driven from an FM insulator to a Weyl semimetal with a minimum number of Weyl points, i.e., two Weyl points in systems without time-reversal symmetry. More importantly, in FM MnBi2Te4 with out-of-plane easy magnetization axis, we found that the band dispersion of the WP evolves from Type-II to Type-III and finally to Type-I when the light intensity increases. Moreover, we show that the profile of the characteristic Fermi arc of Weyl semimetal phase is sensitive to changes in light intensity, which enables efficient manipulation of the Fermi arc length of FM MnBi2Te4 in experiments. In addition, for FM MnBi2Te4 with in-plane easy magnetization axis, the system becomes a type I Weyl semimetal under CPL irradiation. With controllable band dispersion, length of Fermi arc, and minimum number of WPs, our results indicate that CPL-irradiated FM MnBi2Te4 is an ideal platform to study novel transport phenomena in Weyl semimetals with distinct band dispersion. Copyright © 2024, The Authors. All rights reserved.

关键词： Dispersions

Flexible Control of Chiral Superconductivity in Optically Driven Nodal Point Superconductors with Antiferromagnetism

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arXiv 2024年

作者： Ning, Zhen Zeng, Junjie Ma, Da-Shuai Xu, Dong-Hui Wang, Rui Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Center of Quantum Materials and Devices Chongqing University Chongqing400044 China

Recent studies have attracted widespread attention on magnet-superconductor hybrid systems with emergent topological superconductivity. Here, we present the Floquet engineering of realistic two-dimensional topological nodal-point superconductors that are composed of antiferromagnetic monolayers in proximity to an s-wave superconductor. We show that Floquet chiral topological superconductivity arises naturally due to light-induced breaking of the effective time-reversal symmetry. More strikingly, we find that the Floquet chiral topological superconducting phases can be flexibly controlled by irradiating elliptically polarized light, with the photon-dressed quasienergy spectrum carrying different Chern numbers. Such optically switchable topological transition is attributed to the simultaneous creations (or annihilations) of valley pairs. Our findings provide a feasible approach for achieving the Floquet chiral topological superconductivity with flexible tunability, which would draw extensive attention in experiments. Copyright © 2024, The Authors. All rights reserved.

关键词： Superconducting materials

Nanotube-like hard carbon as high-performance anode material for sodium ion hybrid capacitors

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Science China Materials 2018年第2期61卷 285-295页

作者：丁永强杨兵军陈江涛张莉栗军帅李亚丽阎兴斌 Laboratory of Clean Energy Chemistry and Materials State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Key Laboratory of Special Function Materials & Structure Design of the Ministry of Education Key Laboratory for Magnetism & Magnetic Materials of the Ministry of Education and School of Physical Science & Technology Lanzhou University Department of Physics School of Science Lanzhou University of Technology

Sodium ion hybrid capacitors（SIHCs） are of great concern in large-scale energy storage applications due to their good energy-and-power characteristic, as well as abundant reserves and low cost of sodium. However, the sluggish faradaic kinetics of anode materials severely limit the overall electrochemical performance of SIHC devices. Herein, we report an application of nanotube-like hard carbon（NTHC）anode material prepared by high-temperature carbonization（1150℃） of polyaniline（PANI） nanotubes for high-performance SIHCs. As a result, the assembled sodium ion half-cell with NTHC shows a high reversible capacity of 419.5 mA h g^-1at 0.05 A g^-1and a good rate performance of 74.6 mA h g^-1 at 2.5 A g^-1 in a potential window of 0-2 V（vs. Na/Na^＋）. On this basic, a SIHC using such NTHC as anode and a high-capacity activated carbon（APDC） as cathode is fabricated, which exhibits a high energy density of 133.0 W h kg^-1 at 2850 W kg^-1and still remains 100.9 W h kg^-1 at 14,250 W kg^-1. Within the potential range of 1.5-3.5 V, the SIHCs display an outstanding cycling stability tested at 2 A g^-1 with a good capacity retention of 82.5% even after 12,000 cycles.

关键词： sodium ion hybrid capacitor anode hard carbon polyaniline nanotube

Design of Antiferromagnetic Second-order Band Topology with Rotation Topological Invariants in Two Dimensions

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arXiv 2023年

作者： Zhan, Fangyang Qin, Zheng Xu, Dong-Hui Zhou, Xiaoyuan Ma, Da-Shuai Wang, Rui Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Center of Quantum materials and devices Chongqing University Chongqing400044 China

The existence of fractionally quantized topological corner states serves as a key indicator for two-dimensional second-order topological insulators (SOTIs), yet 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 two dimensional systems with antiferromagnetic (AFM) order. We uncover by a minimum lattice model 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 phases can be realized in (MnBi2Te4)(Bi2Te3)m films. Moreover, we demonstrate that the nontrivial corner states are linked to rotation topological invariants under three-fold rotation symmetry C3, resulting in C3-symmetric SOTIs with corner charges fractionally quantized to 3n |e| (mod e). Due to the great recent achievements in (MnBi2Te4)(Bi2Te3)m systems, our results providing reliable material candidates for experimentally accessible AFM higher-order band topology would draw intense attentions. Copyright © 2023, The Authors. All rights reserved.

关键词： Topology