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
Topological superconductors(TSCs)have been widely investigated in recent years due to their novel physics and ability to host Majorana fermions(MFs)which are key to topological quantum computation.Despite the great in...Topological superconductors(TSCs)have been widely investigated in recent years due to their novel physics and ability to host Majorana fermions(MFs)which are key to topological quantum computation.Despite the great interest,only a few compounds have been proposed as candidates of intrinsic TSCs,such as iron-based superconductor FeSe_(0.55)Te_(0.45) and 2M-WS_(2).Among them,quasi-one-dimensional superconductor TaSe_(3) possesses fascinating properties such as its simple stoichiometry,layered nature and chemical stability.Here,using scanning tunneling microscope/spectroscopy(STM/STS),we systematically investigate the topography and electronic structure of TaSe_(3).Our STM/STS measurement reveals large atomically flat,defect-free surfaces suitable for the search of MF;electronic density of states consistent with our angle-resolved photoemission result and band-structure calculations,and a uniform superconducting gap with a typical size of∼0.25 meV.Remarkably,additional edge states are observed in the vicinity of the terrace edge,suggesting they may have a topological origin.Our result proves the coexistence of superconductivity and topological electronic structure in TaSe_(3),making it an intriguing platform to investigate topological superconductivity.展开更多
Dirac semimetals are materials in which the conduction and the valence bands have robust crossing points protected by topology or symmetry. Recently, a new type of Dirac semimetals, so called the Dirac line-node semim...Dirac semimetals are materials in which the conduction and the valence bands have robust crossing points protected by topology or symmetry. Recently, a new type of Dirac semimetals, so called the Dirac line-node semimetals （DLNSs）, have attracted a lot of attention, as they host robust Dirac points along the one-dimensional （1D） lines in the Brillouin zone （BZ）. In this work, using angle-resolved photoemission spectroscopy （ARPES） and first-principles calculations, we systematically investigated the electronic structures of non-symmorphic ZrSiS crystal where we clearly distinguished the surface states from the bulk states. The photon-energy-dependent measurements further prove the existence of Dirac line node along the X-R direction. Remarkably, by in situ surface potassium doping, we clearly observed the different evolutions of the bulk and surface electronic states while proving the robustness of the Dirac line node. Our studies not only reveal the complete electronic structures of ZrSiS, but also demonstrate the method manipulating the electronic structure of the compound.展开更多
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Supported by the National Key R&D Program of China(Grant No.2017YFA0305400)the Shanghai Technology Innovation Action Plan 2020-Integrated Circuit Technology Support Program(Grant No.20DZ1100605)+2 种基金the National Natural Science Foundation of China(Grant Nos.52072168,21733001,51861145201,U1932217,and 11974246)the National Key Basic Research Program of China(Grant No.2018YFA0306200)the Science and Technology Commission of Shanghai Municipality(Grant No.19JC1413900).
文摘Topological superconductors(TSCs)have been widely investigated in recent years due to their novel physics and ability to host Majorana fermions(MFs)which are key to topological quantum computation.Despite the great interest,only a few compounds have been proposed as candidates of intrinsic TSCs,such as iron-based superconductor FeSe_(0.55)Te_(0.45) and 2M-WS_(2).Among them,quasi-one-dimensional superconductor TaSe_(3) possesses fascinating properties such as its simple stoichiometry,layered nature and chemical stability.Here,using scanning tunneling microscope/spectroscopy(STM/STS),we systematically investigate the topography and electronic structure of TaSe_(3).Our STM/STS measurement reveals large atomically flat,defect-free surfaces suitable for the search of MF;electronic density of states consistent with our angle-resolved photoemission result and band-structure calculations,and a uniform superconducting gap with a typical size of∼0.25 meV.Remarkably,additional edge states are observed in the vicinity of the terrace edge,suggesting they may have a topological origin.Our result proves the coexistence of superconductivity and topological electronic structure in TaSe_(3),making it an intriguing platform to investigate topological superconductivity.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0305400)Chinese Academy of Science–Shanghai Science Research Center(Grant No.CAS-SSRC-YH-2015-01)+2 种基金the National Natural Science Foundation of China(Grant No.11674229)the Engineering and Physical Sciences Research Council Platform(Grant No.EP/M020517/1)the Hefei Science–Center Chinese Academy of Sciences(Grant No.2015HSC-UE013)
文摘Dirac semimetals are materials in which the conduction and the valence bands have robust crossing points protected by topology or symmetry. Recently, a new type of Dirac semimetals, so called the Dirac line-node semimetals （DLNSs）, have attracted a lot of attention, as they host robust Dirac points along the one-dimensional （1D） lines in the Brillouin zone （BZ）. In this work, using angle-resolved photoemission spectroscopy （ARPES） and first-principles calculations, we systematically investigated the electronic structures of non-symmorphic ZrSiS crystal where we clearly distinguished the surface states from the bulk states. The photon-energy-dependent measurements further prove the existence of Dirac line node along the X-R direction. Remarkably, by in situ surface potassium doping, we clearly observed the different evolutions of the bulk and surface electronic states while proving the robustness of the Dirac line node. Our studies not only reveal the complete electronic structures of ZrSiS, but also demonstrate the method manipulating the electronic structure of the compound.
