The dual quantum spin Hall insulator(QSHI)is a newly discovered topological state in the two-dimensional(2D)material TaIrTe_(4),which exhibits both a traditional Z_(2)band gap at the charge neutrality point and a Van ...The dual quantum spin Hall insulator(QSHI)is a newly discovered topological state in the two-dimensional(2D)material TaIrTe_(4),which exhibits both a traditional Z_(2)band gap at the charge neutrality point and a Van Hove singularity(VHS)that induces a correlated Z_(2)band gap with weak doping.Inspired by the recent progress in theoretical understanding and experimental measurements,a promising dual QSHI is predicted in the counterpart material of the NbIrTe_(4)monolayer by first-principles calculations.In addition to the well-known band inversion at the charge neutrality point,two new band inversions are found after a charge density wave(CDW)phase transition when the chemical potential is near the VHS:one direct and one indirect Z_(2)band gap.The VHSinduced non-trivial band gap is approximately 10 meV,significantly larger than that of TaIrTe_(4).Furthermore,as the newly generated band gap is mainly dominated by the 4d orbitals of Nb,the electronic correlation effects should be stronger for NbIrTe_(4)than for TaIrTe_(4).Therefore,the dual QSHI state in the NbIrTe_(4)monolayer is expected to provide a strong platform for investigating the interplay between topologies and correlation effects.展开更多
Iron-based superconductor family FeX(X=S,Se,Te)has been one of the research foci in physics and material science due to their record-breaking superconducting temperature(FeSe film)and rich physical phenomena.Recently,...Iron-based superconductor family FeX(X=S,Se,Te)has been one of the research foci in physics and material science due to their record-breaking superconducting temperature(FeSe film)and rich physical phenomena.Recently,FeS,the least studied Fe X compound(due to the difficulty in synthesizing high quality macroscopic crystals)attracted much attention because of its puzzling superconducting pairing symmetry.In this work,combining scanning tunneling microscopy and angle resolved photoemission spectroscopy(ARPES)with sub-micron spatial resolution,we investigate the intrinsic electronic structures of superconducting FeS from individual single crystalline domains.Unlike FeTe or FeSe,FeS remains identical tetragonal structure from room temperature down to 5 K,and the band structures observed can be well reproduced by our ab-initio calculations.Remarkably,mixed with the 1×1 tetragonal metallic phase,we also observe the coexistence of √5×√5 reconstructed insulating phase in the crystal,which not only helps explain the unusual properties of FeS,but also demonstrates the importance of using spatially resolved experimental tools in the study of this compound.展开更多
First-principles calculations have recently been used to develop comprehensive databases of nonmagnetic topological materials that are protected by time-reversal or crystalline symmetry.However,owing to the low symmet...First-principles calculations have recently been used to develop comprehensive databases of nonmagnetic topological materials that are protected by time-reversal or crystalline symmetry.However,owing to the low symmetry requirement of Weyl points,a symmetry-based approach to identifying topological states cannot be applied to Weyl semimetals(WSMs).To date,WSMs with Weyl points in arbitrary positions are absent from the well-known databases.展开更多
The success of topological band theory and symmetry-based topological classification significantly advances our understanding of the Berry phase.Based on the critical concept of topological obstruction,efficient theor...The success of topological band theory and symmetry-based topological classification significantly advances our understanding of the Berry phase.Based on the critical concept of topological obstruction,efficient theoretical frameworks,including topological quantum chemistry and symmetry indicator theory,were developed,making a massive characterization of real materials possible.However,the classification of magnetic materials often involves the complexity of their unknown magnetic structures,which are often hard to know from experiments,thus,hindering the topological classification.In this paper,we design a high-throughput workflow to classify magnetic topological materials by automating the search for collinear magnetic structures and the characterization of their topological natures.We computed 1049 chosen transition-metal compounds(TMCs)without oxygen and identified 64 topological insulators and 53 semimetals,which become 73 and 26 when U correction is further considered.Due to the lack of magnetic structure information from experiments,our high-throughput predictions provide insightful reference results and make the step toward a complete diagnosis of magnetic topological materials.展开更多
基金supported by the National Key R&D Program of China(Grant No.2021YFB3501503)the National Natural Science Foundation of China(Grant Nos.52271016 and 52188101)the Foundation of Liaoning Province(Grant No.XLYC2203080)。
文摘The dual quantum spin Hall insulator(QSHI)is a newly discovered topological state in the two-dimensional(2D)material TaIrTe_(4),which exhibits both a traditional Z_(2)band gap at the charge neutrality point and a Van Hove singularity(VHS)that induces a correlated Z_(2)band gap with weak doping.Inspired by the recent progress in theoretical understanding and experimental measurements,a promising dual QSHI is predicted in the counterpart material of the NbIrTe_(4)monolayer by first-principles calculations.In addition to the well-known band inversion at the charge neutrality point,two new band inversions are found after a charge density wave(CDW)phase transition when the chemical potential is near the VHS:one direct and one indirect Z_(2)band gap.The VHSinduced non-trivial band gap is approximately 10 meV,significantly larger than that of TaIrTe_(4).Furthermore,as the newly generated band gap is mainly dominated by the 4d orbitals of Nb,the electronic correlation effects should be stronger for NbIrTe_(4)than for TaIrTe_(4).Therefore,the dual QSHI state in the NbIrTe_(4)monolayer is expected to provide a strong platform for investigating the interplay between topologies and correlation effects.
基金Project supported by CAS-Shanghai Science Research Center,China(Grant No.CAS-SSRC-YH-2015-01)the National Key R&D Program of China(Grant No.2017YFA0305400)+4 种基金the National Natural Science Foundation of China(Grant Nos.11674229,11227902,and 11604207)the EPSRC Platform Grant(Grant No.EP/M020517/1)Hefei Science Center,Chinese Academy of Sciences(Grant No.2015HSC-UE013)Science and Technology Commission of Shanghai Municipality,China(Grant No.14520722100)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB04040200)。
文摘Iron-based superconductor family FeX(X=S,Se,Te)has been one of the research foci in physics and material science due to their record-breaking superconducting temperature(FeSe film)and rich physical phenomena.Recently,FeS,the least studied Fe X compound(due to the difficulty in synthesizing high quality macroscopic crystals)attracted much attention because of its puzzling superconducting pairing symmetry.In this work,combining scanning tunneling microscopy and angle resolved photoemission spectroscopy(ARPES)with sub-micron spatial resolution,we investigate the intrinsic electronic structures of superconducting FeS from individual single crystalline domains.Unlike FeTe or FeSe,FeS remains identical tetragonal structure from room temperature down to 5 K,and the band structures observed can be well reproduced by our ab-initio calculations.Remarkably,mixed with the 1×1 tetragonal metallic phase,we also observe the coexistence of √5×√5 reconstructed insulating phase in the crystal,which not only helps explain the unusual properties of FeS,but also demonstrates the importance of using spatially resolved experimental tools in the study of this compound.
基金This work was financially supported by the ERC Advanced Grant No.291472‘Idea Heusler’,ERC Advanced Grant No.742068‘TOPMAT’We also acknowledge funding by the DFG through SFB 1143(project ID 247310070)the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter-ct.qmat(EXC 2147,project ID 39085490).
文摘First-principles calculations have recently been used to develop comprehensive databases of nonmagnetic topological materials that are protected by time-reversal or crystalline symmetry.However,owing to the low symmetry requirement of Weyl points,a symmetry-based approach to identifying topological states cannot be applied to Weyl semimetals(WSMs).To date,WSMs with Weyl points in arbitrary positions are absent from the well-known databases.
基金supported by the National Key R&D Program of China(2017YFA0305400 and 2019YFA0704900)Chinese Academy of Sciences-Shanghai Science Research Center(CAS-SSRC-YH2015-01)+9 种基金Double First-Class Initiative Fund of Shanghai Tech Universitythe support from the Engineering and Physical Sciences Research Council Platform Grant(EP/M020517/1)the Major Research Plan of the National Natural Science Foundation of China(NSFC,92065201)Shanghai Municipal Science and Technology Major Project(2018SHZDZX02)the support from the NSFC(52088101 and 11974394)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB33000000)the support from Shanghai Committee of Science and Technology(22ZR1441800)Shanghai-XFEL Beamline Project(SBP)(31011505505885920161A2101001)the support from the NSFC(12004248)and the support from the NSFC(12104304)Shanghai Sailing Program(20YF1430500)。
基金This work is supported by the Shanghai Technology Innovation Action Plan 2020-Integrated Circuit Technology Support Program(Project No.20DZ1100605)the National Natural Science Foundation of China under Grant No.11874263,Sino-German mobility program(M-0006)+1 种基金the National Key R&D Program of China(2017YFE0131300)W.S.wants to thank the financial support of the Science and Technology Commission of Shanghai Municipality(STCSM)(Grant No.22ZR1441800),Shanghai-XFEL Beamline Project(SBP)(31011505505885920161A2101001)。
文摘The success of topological band theory and symmetry-based topological classification significantly advances our understanding of the Berry phase.Based on the critical concept of topological obstruction,efficient theoretical frameworks,including topological quantum chemistry and symmetry indicator theory,were developed,making a massive characterization of real materials possible.However,the classification of magnetic materials often involves the complexity of their unknown magnetic structures,which are often hard to know from experiments,thus,hindering the topological classification.In this paper,we design a high-throughput workflow to classify magnetic topological materials by automating the search for collinear magnetic structures and the characterization of their topological natures.We computed 1049 chosen transition-metal compounds(TMCs)without oxygen and identified 64 topological insulators and 53 semimetals,which become 73 and 26 when U correction is further considered.Due to the lack of magnetic structure information from experiments,our high-throughput predictions provide insightful reference results and make the step toward a complete diagnosis of magnetic topological materials.
