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
The recently discovered high-temperature superconductor La_(3)Ni_(2)O_(7)under high pressure has sparked considerable debate.Central controversies revolve around whether interlayer or intralayer pairing mechanisms dom...The recently discovered high-temperature superconductor La_(3)Ni_(2)O_(7)under high pressure has sparked considerable debate.Central controversies revolve around whether interlayer or intralayer pairing mechanisms dominate and whether hybridization plays a crucial role in establishing superconductivity.However,experimental clarification remains challenging due to the limitations of state-of-the-art techniques under high-pressure conditions.Here,we propose that quasiparticle tunneling and Andreev reflection could offer practical methods to differentiate pairing scenarios.Specifically,we predict that hybridization between the d_(x^(2)-y^(2))metallic bands and the strongly renormalized flat d_(z^(2))quasiparticle bands may induce an asymmetric Fano line shape.In the superconducting state,we show that Andreev reflection would be significantly suppressed in interlayer pairing superconductivity with limited interlayer hopping.We recommend future experiments to test these predictions and shed light on the fundamental physics of superconducting La_(3)Ni_(2)O_(7)and other multi-layer nickelate superconductors.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supported by the National Natural Science Foundation of China(Grant No.12474136)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33010100)the National Key Research and Development Program of China(Grant No.2022YFA1402203)。
文摘The recently discovered high-temperature superconductor La_(3)Ni_(2)O_(7)under high pressure has sparked considerable debate.Central controversies revolve around whether interlayer or intralayer pairing mechanisms dominate and whether hybridization plays a crucial role in establishing superconductivity.However,experimental clarification remains challenging due to the limitations of state-of-the-art techniques under high-pressure conditions.Here,we propose that quasiparticle tunneling and Andreev reflection could offer practical methods to differentiate pairing scenarios.Specifically,we predict that hybridization between the d_(x^(2)-y^(2))metallic bands and the strongly renormalized flat d_(z^(2))quasiparticle bands may induce an asymmetric Fano line shape.In the superconducting state,we show that Andreev reflection would be significantly suppressed in interlayer pairing superconductivity with limited interlayer hopping.We recommend future experiments to test these predictions and shed light on the fundamental physics of superconducting La_(3)Ni_(2)O_(7)and other multi-layer nickelate superconductors.
