The alkali adatoms with controlled coverage on the surface have been demonstrated to effectively tune the surface band of quantum materials through in situ electron doping.However,the interplay of orderly arranged alk...The alkali adatoms with controlled coverage on the surface have been demonstrated to effectively tune the surface band of quantum materials through in situ electron doping.However,the interplay of orderly arranged alkali adatoms with the surface states of quantum materials remains unexplored.Here,by using low-temperature scanning tunneling microscopy/spectroscopy(STM/S),we observed the emergent 3×3 super modulation of electronic states on the√3×√3R30°(R3)Cs ordered surface of kagome superconductor CsV_(3)Sb_(5).The nondispersive 3×3 superlattice at R3 ordered surface shows contrast inversion in positive and negative differential conductance maps,indicating a charge order origin.The 3×3 charge order is suppressed with increasing temperature and undetectable at a critical temperature of~62 K.Furthermore,in the Ta substituted sample CsV_(2.6)Ta_(0.4)Sb_(5),where long-range 2×2×2 charge density wave is significantly suppressed,the 3×3 charge order on the R3 ordered surface becomes blurred and much weaker than that in the undoped sample.It indicates that the 3×3 charge order on the R3 ordered surface is directly correlated to the bulk charge density waves in CsV_(3)Sb_(5).Our work provides a new platform for understanding and manipulating the cascade of charge orders in kagome superconductors.展开更多
V-based kagome materials AV_(3)Sb_(5)(A=K,Rb,Cs)have attracted much attention due to their novel properties such as unconventional superconductivity,giant anomalous Hall effect,charge density wave(CDW)and pair density...V-based kagome materials AV_(3)Sb_(5)(A=K,Rb,Cs)have attracted much attention due to their novel properties such as unconventional superconductivity,giant anomalous Hall effect,charge density wave(CDW)and pair density wave.Except for the 2a_(0)×2a_(0)CDW(charge density wave with in-plane 2×2 superlattice modulation)in AV_(3)Sb_(5),an additional 1×4(4a_(0))unidirectional stripe order has been observed at the Sb surface of Rb V3 Sb5 and CsV_(3)Sb_(5).However,the stability and electronic nature of the 4a_(0) stripe order remain controversial and unclear.Here,by using low-temperature scanning tunneling microscopy/spectroscopy(STM/S),we systematically study the 4a_(0) stripe order on the Sb-terminated surface of CsV_(3)Sb_(5).We find that the 4a_(0) stripe order is visible in a large energy range.The STM images with positive and negative bias show contrast inversion,which is the hallmark for the Peierls-type CDW.In addition,below the critical temperature about 60 K,the 4a_(0)stripe order keeps unaffected against the topmost Cs atoms,point defects,step edges and magnetic field up to 8 T.Our results provide experimental evidences on the existence of unidirectional CDW in CsV_(3)Sb_(5).展开更多
Vortices and bound states offer an effective means of comprehending the electronic properties of superconductors.Recently,surface-dependent vortex core states have been observed in the newly discovered kagome supercon...Vortices and bound states offer an effective means of comprehending the electronic properties of superconductors.Recently,surface-dependent vortex core states have been observed in the newly discovered kagome superconductors CsV_(3)Sb_(5).Although the spatial distribution of the sharp zero energy conductance peak appears similar to Majorana bound states arising from the superconducting Dirac surface states,its origin remains elusive.In this study,we present observations of tunable vortex bound states(VBSs)in two chemically-doped kagome superconductors Cs(V_(1-x)Tr_(x))_(3)Sb_(5)(Tr=Ta or Ti),using low-temperature scanning tunneling microscopy/spectroscopy.The CsV_(3)Sb_(5)-derived kagome superconductors exhibit full-gap-pairing superconductivity accompanied by the absence of long-range charge orders,in contrast to pristine CsV_(3)Sb_(5).Zero-energy conductance maps demonstrate a field-driven continuous reorientation transition of the vortex lattice,suggesting multiband superconductivity.The Ta-doped CsV_(3)Sb_(5)displays the conventional cross-shaped spatial evolution of Caroli-de Gennes-Matricon bound states,while the Tidoped CsV_(3)Sb_(5)exhibits a sharp,non-split zero-bias conductance peak(ZBCP)that persists over a long distance across the vortex.The spatial evolution of the non-split ZBCP is robust against surface effects and external magnetic field but is related to the doping concentrations.Our study reveals the tunable VBSs in multiband chemically-doped CsV_(3)Sb_(5)system and offers fresh insights into previously reported Y-shaped ZBCP in a non-quantum-limit condition at the surface of kagome superconductor.展开更多
基金Project supported by the National Key Research and Development Project of China(Grant Nos.2022YFA1204100 and 2019YFA0308500)the National Natural Science Foundation of China(Grant No.62488201)+1 种基金the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-003)the Innovation Program of Quantum Science and Technology(Grant No.2021ZD0302700)。
文摘The alkali adatoms with controlled coverage on the surface have been demonstrated to effectively tune the surface band of quantum materials through in situ electron doping.However,the interplay of orderly arranged alkali adatoms with the surface states of quantum materials remains unexplored.Here,by using low-temperature scanning tunneling microscopy/spectroscopy(STM/S),we observed the emergent 3×3 super modulation of electronic states on the√3×√3R30°(R3)Cs ordered surface of kagome superconductor CsV_(3)Sb_(5).The nondispersive 3×3 superlattice at R3 ordered surface shows contrast inversion in positive and negative differential conductance maps,indicating a charge order origin.The 3×3 charge order is suppressed with increasing temperature and undetectable at a critical temperature of~62 K.Furthermore,in the Ta substituted sample CsV_(2.6)Ta_(0.4)Sb_(5),where long-range 2×2×2 charge density wave is significantly suppressed,the 3×3 charge order on the R3 ordered surface becomes blurred and much weaker than that in the undoped sample.It indicates that the 3×3 charge order on the R3 ordered surface is directly correlated to the bulk charge density waves in CsV_(3)Sb_(5).Our work provides a new platform for understanding and manipulating the cascade of charge orders in kagome superconductors.
基金financially supported by the National Key Research and Development Project of China(Grant Nos.2018YFA0305800 and 2019YFA0308500)the National Natural Science Foundation of China(Grant Nos.61888102and 52022105)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB30000000 and XDB28000000)CAS Project for Young Scientists in Basic Research(Grant No.YSBR-003)the University of Chinese Academy of Sciences。
文摘V-based kagome materials AV_(3)Sb_(5)(A=K,Rb,Cs)have attracted much attention due to their novel properties such as unconventional superconductivity,giant anomalous Hall effect,charge density wave(CDW)and pair density wave.Except for the 2a_(0)×2a_(0)CDW(charge density wave with in-plane 2×2 superlattice modulation)in AV_(3)Sb_(5),an additional 1×4(4a_(0))unidirectional stripe order has been observed at the Sb surface of Rb V3 Sb5 and CsV_(3)Sb_(5).However,the stability and electronic nature of the 4a_(0) stripe order remain controversial and unclear.Here,by using low-temperature scanning tunneling microscopy/spectroscopy(STM/S),we systematically study the 4a_(0) stripe order on the Sb-terminated surface of CsV_(3)Sb_(5).We find that the 4a_(0) stripe order is visible in a large energy range.The STM images with positive and negative bias show contrast inversion,which is the hallmark for the Peierls-type CDW.In addition,below the critical temperature about 60 K,the 4a_(0)stripe order keeps unaffected against the topmost Cs atoms,point defects,step edges and magnetic field up to 8 T.Our results provide experimental evidences on the existence of unidirectional CDW in CsV_(3)Sb_(5).
基金supported by the National Natural Science Foundation of China(61888102,52022105,92065109,and 12174428)the National Key Research and Development Projects of China(2022YFA1204100,2018YFA0305800,2019YFA0308500,2020YFA0308800,and 2022YFA1403400)+4 种基金the CAS Project for Young Scientists in Basic Research(YSBR-003 and 2022YSBR-048)the Innovation Program of Quantum Science and Technology(2021ZD0302700)the financial support from the European Research Council(ERC Consolidator Grant “Nonlinear Topo”,No.815869)ISF-Singapore-Israel Research Grant(3520/20)supported by the US DOE,Basic Energy Sciences(DE-FG02-99ER45747)。
文摘Vortices and bound states offer an effective means of comprehending the electronic properties of superconductors.Recently,surface-dependent vortex core states have been observed in the newly discovered kagome superconductors CsV_(3)Sb_(5).Although the spatial distribution of the sharp zero energy conductance peak appears similar to Majorana bound states arising from the superconducting Dirac surface states,its origin remains elusive.In this study,we present observations of tunable vortex bound states(VBSs)in two chemically-doped kagome superconductors Cs(V_(1-x)Tr_(x))_(3)Sb_(5)(Tr=Ta or Ti),using low-temperature scanning tunneling microscopy/spectroscopy.The CsV_(3)Sb_(5)-derived kagome superconductors exhibit full-gap-pairing superconductivity accompanied by the absence of long-range charge orders,in contrast to pristine CsV_(3)Sb_(5).Zero-energy conductance maps demonstrate a field-driven continuous reorientation transition of the vortex lattice,suggesting multiband superconductivity.The Ta-doped CsV_(3)Sb_(5)displays the conventional cross-shaped spatial evolution of Caroli-de Gennes-Matricon bound states,while the Tidoped CsV_(3)Sb_(5)exhibits a sharp,non-split zero-bias conductance peak(ZBCP)that persists over a long distance across the vortex.The spatial evolution of the non-split ZBCP is robust against surface effects and external magnetic field but is related to the doping concentrations.Our study reveals the tunable VBSs in multiband chemically-doped CsV_(3)Sb_(5)system and offers fresh insights into previously reported Y-shaped ZBCP in a non-quantum-limit condition at the surface of kagome superconductor.
