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
By using scanning tunneling microscopy,we investigated the electronic evolution of T_(d)-WTe_(2) via in-situ surface alkali K atoms deposition.The T_(d)-WTe_(2) surface is electron doped upon K deposition,and as the K...By using scanning tunneling microscopy,we investigated the electronic evolution of T_(d)-WTe_(2) via in-situ surface alkali K atoms deposition.The T_(d)-WTe_(2) surface is electron doped upon K deposition,and as the K coverage increases,two gaps are sequentially opened near Fermi energy,which probably indicates that two phase transitions concomitantly occur during electron doping.The two gaps both show a dome-like dependence on the K coverage.While the bigger gap shows no prominent dependence on the magnetic field,the smaller one can be well suppressed and thus possibly corresponds to the superconducting transition.This work indicates that T_(d)-WTe_(2) exhibits rich quantum states closely related to the carrier concentration.展开更多
Hg Te(111)surface is comprehensively studied by scanning tunneling microscopy/spectroscopy(STS).In addition to th√e prim√itive(1×1)√hexagonal lattice,six reconstructed surface structures are observed:(2×2...Hg Te(111)surface is comprehensively studied by scanning tunneling microscopy/spectroscopy(STS).In addition to th√e prim√itive(1×1)√hexagonal lattice,six reconstructed surface structures are observed:(2×2),2×1,4×1,3×(1/2)3,2(1/2)2×2 and(1/2)11×2.The(2×2)reconstructed lattice maintains the primitive hexagonal symmetry,whi√le the lattices of the other five reconstructions are rectangular.Moreover,the topographic features of the3×(1/2)3 reconstruction are bias dependent,indicating that they have both topographic and electronic origins.The STSs obtained at different reconstructed surfaces show a universal dip feature with size~100 mV,which may be attributed to the surface distortion.Our results reveal the atomic structure and complex reconstructions of the cleaved Hg Te(111)surfaces,which paves the way to understand the rich properties of Hg Te crystal.展开更多
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.
基金financially supported by the National Natural Science Foundation of China(Grants Nos.11790311,92165205,51902152,11874210,and 11774149)the National Key R&D Program of China(Grants No.2021YFA1400403)。
文摘By using scanning tunneling microscopy,we investigated the electronic evolution of T_(d)-WTe_(2) via in-situ surface alkali K atoms deposition.The T_(d)-WTe_(2) surface is electron doped upon K deposition,and as the K coverage increases,two gaps are sequentially opened near Fermi energy,which probably indicates that two phase transitions concomitantly occur during electron doping.The two gaps both show a dome-like dependence on the K coverage.While the bigger gap shows no prominent dependence on the magnetic field,the smaller one can be well suppressed and thus possibly corresponds to the superconducting transition.This work indicates that T_(d)-WTe_(2) exhibits rich quantum states closely related to the carrier concentration.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0301003 and 2016YFA0300403the National Natural Science Foundation of China under Grant Nos 11521404,11634009,U1632102,11504230,11674222,11574202,11674226,11574201 and U1632272
文摘Hg Te(111)surface is comprehensively studied by scanning tunneling microscopy/spectroscopy(STS).In addition to th√e prim√itive(1×1)√hexagonal lattice,six reconstructed surface structures are observed:(2×2),2×1,4×1,3×(1/2)3,2(1/2)2×2 and(1/2)11×2.The(2×2)reconstructed lattice maintains the primitive hexagonal symmetry,whi√le the lattices of the other five reconstructions are rectangular.Moreover,the topographic features of the3×(1/2)3 reconstruction are bias dependent,indicating that they have both topographic and electronic origins.The STSs obtained at different reconstructed surfaces show a universal dip feature with size~100 mV,which may be attributed to the surface distortion.Our results reveal the atomic structure and complex reconstructions of the cleaved Hg Te(111)surfaces,which paves the way to understand the rich properties of Hg Te crystal.
