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From atomic semimetal to topological nontrivial insulator

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

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Design monolayer iodinenes based on halogen bond and tiling theory

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Physical Review B 2024年第12期109卷 125423-125423页

作者： Kejun Yu Yichen Liu Botao Fu Run-Wu Zhang Da-shuai Ma Xiao-ping Li Zhi-Ming Yu Cheng-Cheng Liu 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 Lab of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China College of Physics and Electronic Engineering Center for Computational Sciences Sichuan Normal University Chengdu 610068 China Institute for Structure and Function and Department of Physics and 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 School of Physical Science and Technology Inner Mongolia University Hohhot 010021 China

Xenes, two-dimensional (2D) monolayers composed of a single element, with graphene as a typical representative, have attracted widespread attention. Most of the previous Xenes, X from group-IIIA to group-VIA elements, have bonding characteristics of covalent bonds. In this paper, we unveil the pivotal role of a halogen bond, which is a distinctive type of bonding with interaction strength between that of a covalent bond and a van der Waals interaction, in 2D group-VIIA monolayers. Combing the ingenious non-edge-to-edge tiling theory and state-of-the-art ab initio method with refined local density functional M06-L, we provide a precise and effective bottom-up construction of 2D iodine monolayer sheets, iodinenes, primarily governed by halogen bonds, and successfully design a category of stable iodinenes encompassing herringbone, Pythagorean, gyrated truncated hexagonal, i.e., diatomic kagome, and gyrated hexagonal tiling patterns. These iodinene structures exhibit a wealth of properties, such as nontrivial topology, flat bands and fascinating optical characteristics, offering valuable insights and guidance for future experimental investigations. Our paper not only unveils the unexplored halogen bonding mechanism in 2D materials but also opens an avenue for designing other noncovalent bonding 2D materials.

关键词： Electronic structure Structural properties Topological materials 2-dimensional systems Two-dimensional electron system Density functional theory

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Gyrotropic Magnetic Effect in Black Phosphorus Irradiated with Bicircular Light

arXiv

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arXiv 2024年

作者： Zhan, Fangyang Jin, Xin Ma, Da-Shuai Fan, Jing Yu, Peng Xu, Dong-Hui Wang, Rui Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China College of Mathematics and Statistics Chongqing University Chongqing400044 China College of Physics and Electronic Engineering Chongqing Normal University Chongqing400044 China Center of Quantum materials and devices Chongqing University Chongqing400044 China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen518055 China

The gyrotropic magnetic effect, manifesting as a gyropropic current under a slowly-varying magnetic field, represents a fundamental property of Bloch electrons on the Fermi surface;however, it has not been observed in experiments. Here, we theoretically propose that Floquet engineering with bicircular light (BCL), which is a superposition of two opposite chiral waves of circularly polarized light with an integer frequency ratio, presents a fascinating strategy to generate and manipulate the gyrotropic magnetic effect in nodal line semimetals. The tailoring spatial symmetry of BCL irradiation can induce a topological transition from a nodal line semimetallic phase to a Weyl semimetallic phase characterized by a minimum number of misaligned Weyl nodes, resulting in the generation of gyrotropic current when a slowly oscillating magnetic field is applied. Moreover, using first-principles calculations, we show that the compressed black phosphorus under irradiation of BCL is an ideal candidate to realize the large gyropropic current with great advantages. Our work not only broadens potential candidate materials for achieving the experimentally accessible gyropropic current, but also provides deeper insights into the interplay between topological phenomena and light manipulation of symmetries. Copyright © 2024, The Authors. All rights reserved.

关键词： Topology

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In-plane canted ferromagnetism, intrinsic Weyl fermions, and large anomalous Hall effect in the kagome semimetal Rh3Sn2S2

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Physical Review B 2023年第17期108卷 174430-174430页

作者： Meng-Xin Wu Yu-Hao Wei Da-Shuai Ma Peng Wang Nan Gao Shao-Yi Wu Min-Quan Kuang Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics and School of Physical Science and Technology Southwest University Chongqing 400715 People's Republic of China Institute for Structure and Function Department of Physics and 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 School of Material Science and Engineering Taizhou University Taizhou 318000 People's Republic of China Department of Applied Physics School of Physics University of Electronic Science and Technology of China Chengdu 611731 People's Republic of China

Magnetic Weyl semimetals can reveal a renowned electronic transport phenomenon, i.e., the anomalous Hall effect due to the intrinsic Berry curvature promoted by the Weyl fermions. Here, the layered kagome compound Rh3Sn2S2 is identified as a ferromagnetic Weyl semimetal by first-principles calculations. When the spin-orbit coupling is absent, three sets of nontrivial Weyl nodal lines emerge in the spin-up channel, while the spin-down bands are fully gapped. The obtained magnetocrystalline anisotropy energy indicates that Rh3Sn2S2 has an in-plane canted magnetic order with a 30∘ angle to the a axis. As a consequence, the spin-orbit coupling breaks the time-reversal symmetry, and the broken Weyl nodal lines give birth to one pair of Weyl points near the Fermi level. The chiral Weyl nodes, protected by the space inversion and the C3z-rotation symmetry, act as the monopole source and sink of the Berry curvature and boost a large anomalous Hall conductivity approaching 580 Ω−1cm−1. This work unveils the magnetic, electronic, and topological properties as well as the anomalous Hall effect of Rh3Sn2S2, which will facilitate future research on the unexplored topological phenomena in Rh3Sn2S2.

关键词： Anomalous Hall effect Ferromagnetism Kagome lattice Weyl semimetal Electronic structure First-principles calculations Symmetries

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Chiral-Flux-Phase-Based Topological Superconductivity in Kagome Systems with Mixed Edge Chiralities

arXiv

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arXiv 2023年

作者： Zeng, Junjie Li, Qingming Yang, Xun Xu, Dong-Hui Wang, Rui Institute for Structure and Function Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Department of Physics Shijiazhuang University Hebei Shijiazhuang050035 China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen518055 China Center of Quantum materials and devices Chongqing University Chongqing400044 China

Recent studies have attracted intense attention on the quasi-2D kagome superconductors AV3Sb5 (A = K, Rb, and Cs) where the unexpected chiral flux phase (CFP) associates with the spontaneous time-reversal symmetry breaking in charge density wave (CDW) states. Here, commencing from the 2-by-2 CDW phases, we bridge the gap between topological superconductivity (TSC) and time-reversal asymmetric CFP in kagome systems. Several chiral TSC states featuring distinct Chern numbers emerge for an s-wave or a d-wave superconducting pairing symmetry. Importantly, these CFP-based TSC phases possess unique gapless edge modes with mixed chiralities (i.e., both positive and negative chiralities), but with the net chiralities consistent with the Bogoliubovde Gennes Chern numbers. We further study the transport properties of a two-terminal junction, using Chern insulator or normal metal leads via atomic Green’s function method with Landauer-Büttiker formalism. In both cases, the normal electron tunneling and the crossed Andreev reflection oscillate as the chemical potential changes, but together contribute to plateau transmissions (1 and 3/2, respectively). These behaviors can be regarded as the signature of a topological superconductor hosting edge states with mixed chiralities. © 2023, CC BY-NC-SA.

关键词： Topology

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Realization of charge-four Weyl point in fermionic systems

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Physical Review B 2023年第7期108卷 075130-075130页

作者： Xiaoliang Xiao Yuanjun Jin Da-Shuai Ma Weixiang Kong Jing Fan Rui Wang Xiaozhi Wu Institute for Structure and Function & Department of Physics Chongqing University Chongqing 400044 People's Republic of China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore Center of Quantum materials and devices Chongqing University Chongqing 400044 People's Republic of China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen 518055 People's Republic of China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing 401331 People's Republic of China

Unconventional quasiparticles of a twofold band degeneracy with |C|=4, named as charge-four Weyl point (CFWP), have been revealed in bosonic and artificial systems, while it is challenging in fermionic systems because of nonnegligible spin-orbit coupling. Herein, we propose a carbon allotrope, termed cP-C24, as an ideal platform to realize CFWP in the nonrelativistic limit. Besides one CFWP (C=+4), there are also eight type-I Weyl points (C=+1) and twelve type-II Weyl nodes (C=−1), making the topological charge in the whole Brillouin zone to be neutral. The characteristic quadruple helicoid surface states of CFWP are presented. Our work offering the avenue of CFWP in fermionic systems would absolutely advance the research on the chirality-dependent physical properties associated with unconventional topological quasiparticles.

关键词： Fermions Symmetry protected topological states 3-dimensional systems Crystal structures First-principles calculations Symmetries in condensed matter Wannier function methods k dot p method

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On the existence of a proton halo in 22Al

arXiv

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arXiv 2024年

作者： Zhang, K.Y. Pan, C. Wang, Sibo Institute of Nuclear Physics and Chemistry China Academy of Engineering Physics Sichuan Mianyang621900 China Department of Physics Anhui Normal University Anhui Wuhu241000 China Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing401331 China

More and more halo nuclei or candidates have been identified or suggested in experiments in recent years. It was declared that the halo structure of 22Al is revealed by the large isospin asymmetry in 22Si/22O mirror Gamow-Teller transitions [Phys. Rev. Lett. 125, 192503 (2020)]. We highlight that a significant mirror asymmetry already exists between wave functions of the likely unbound nucleus 22Si and the doubly-magic nucleus 22O, which largely explains the observed asymmetry in the transitions. Furthermore, these transitions involve only the 1+ excited states of the daughter nuclei 22Al and 22F. The 1+ state of 22Al cannot be considered a halo state due to its proton-unbound nature. An analysis of the spin-parity suggests that a weakly bound 2s1/2 valence proton in the ground-state 22Al is improbable. To investigate the shell structure for the ground state of 22Al, we employ the state-of-the-art deformed and triaxial relativistic Hartree-Bogoliubov theories in continuum. We find that a small s-wave component of 5% appears for the weakly bound valence proton in 22Al only when triaxial deformation is considered. While the examination of densities and rms radii indicates that this small s-wave component is insufficient to form a discernible proton halo in 22Al, slightly larger 2s1/2 occupations have been reported in other recent theoretical results. The question of how many low- components are sufficient to form a proton halo in the presence of the Coulomb barrier remains open. Thus, future measurements of reaction or interaction cross sections and momentum distributions of breakup fragments are highly desirable to verify whether 22Al is a halo nucleus. © 2024, CC BY.

关键词： Ground state

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Tailoring Quadrupole Topological Insulators with Periodic Driving and Disorder

arXiv

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arXiv 2022年

作者： Ning, Zhen Fu, Bo Xu, Dong-Hui Wang, Rui Institute for Structure and Function Department of Physics Chongqing University Chongqing400044 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing400044 China Department of Physics The University of Hong Kong Pokfulam Road Hong Kong Department of Physics Hubei University Wuhan430062 China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing400044 China Center of Quantum Materials and Devices Chongqing University Chongqing400044 China

The quadrupole topological insulator (QTI) has attracted intense studies as a prototype of symmetry-protected higher-order topological phases of matter with a quantized quadrupole moment. The realization of QTIs has been reported in various static settings with periodic structures. Here, we theoretically investigate topological phase transitions and establish the QTI phase in a periodically driven system with disorder. In the clean limit, the Floquet QTI phase emerges from a topologically trivial band structure driven by elliptically polarized irradiation. More strikingly, starting from a pure and static system with trivial topology, we unveil an intriguing QTI phase which necessitates the simultaneous presence of disorder and periodic driving. Furthermore, we reveal that particle-hole symmetry is sufficient to protect the QTI. Our work not only establishes a new strategy to design QTIs but also enriches the symmetry-protected mechanism of higher-order topology. Copyright © 2022, The Authors. All rights reserved.

关键词： Topological insulators

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Hadron-quark phase transition in neutron star by combining the relativistic Brueckner-Hartree-Fock theory and Dyson-Schwinger equation approach

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Physical Review D 2023年第10期107卷 103009-103009页

作者： Pianpian Qin Zhan Bai Sibo Wang Chencan Wang Si-xue Qin Department of Physics and Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing 401331 China Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100190 China School of Physics and Astronomy Sun Yat-Sen University Zhuhai 519082 China

Starting from the relativistic Brueckner-Hartree-Fock theory for nuclear matter and the Dyson-Schwinger equation approach for quark matter, the possible hadron-quark phase transition in the interior of a neutron star is explored. The first-order phase transition and crossover are studied by performing the Maxwell construction and three-window construction respectively. The mass-radius relation and the tidal deformability of the hybrid star are calculated and compared to the joint mass-radius observation of a neutron star and the constraints from gravitational wave detection. For the Maxwell construction, no stable quark core is found in the interior of a neutron star. For the three-window construction, the parameters of the smooth interpolation function are chosen in such a way to keep the thermodynamic stability and lead to a moderate crossover density region. To support a two-solar-mass neutron star under the three-window construction, the effective width of medium screening effects in quark matter should be around 0.35 GeV.

关键词： Nuclear matter in neutron stars QCD phase transitions

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Hourglass phonons jointly protected by symmorphic and nonsymmorphic symmetries

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Physical Review B 2021年第6期104卷 L060301-L060301页

作者： Baobing Zheng Fangyang Zhan Xiaozhi Wu Rui Wang Jing Fan College of Physics and Optoelectronic Technology & Advanced Titanium Alloys and Functional Coatings Cooperative Innovation Center Baoji University of Arts and Sciences Baoji 721016 People's Republic of China Institute for Structure and Function & Department of Physics Chongqing University Chongqing 400044 People's Republic of China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing 400044 People's Republic of China Center for Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen 518055 People's Republic of China

Hourglass dispersion is generally believed to be solely protected by nonsymmorphic symmetries, because these symmetries can introduce high-dimensional projective representations. Here, based on symmetry arguments, we propose that the hourglass dispersion can be jointly protected by symmorphic and nonsymmorphic symmetries, instead of the conventional nonsymmorphic symmetry. Moreover, using first-principles calculations, we realize our proposal in the phonon spectra of realistic materials that share an antiperovskite structure with space group P4/nmm. Importantly, the neck points of these hourglass dispersions trace out two nodal rings tangential to four nodal lines, forming a unique hourglass nodal cage in the bulk Brillouin zone. The Berry phase analysis reveals the nontrivial topology of these nodal rings and nodal lines. Furthermore, nontrivial surface states and isofrequency surface arcs are visible, facilitating their experimental confirmation of such exotic quasiparticles. work not only offers different insights into the hourglass dispersion, but also expands aspects for studying promising topological quasiparticles in condensed-matter systems.

关键词： Electronic structure Lattice dynamics Phonons Symmetry protected topological states Node-line semimetals First-principles calculations

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