Fermiology and Origin of Tc Enhancement in a Kagome Superconductor Cs(V1-xNbx)3Sb5

Abstract

Kagome metals AV3Sb5 (A = K, Rb, and Cs) exhibit a characteristic superconducting ground state coexisting with charge-density wave (CDW), whereas the mechanisms of the superconductivity and CDW have yet to be clarified. Here we report a systematic ARPES study of Cs(V1-xNbx)3Sb5 as a function of Nb content x, where isovalent Nb substitution causes an enhancement of superconducting transition temperature (Tc) and the reduction of CDW temperature (TCDW). We found that the Nb substitution shifts the Sb-derived electron band at the Gamma point downward and simultaneously moves the V-derived band around the M point upward to lift up the saddle point (SP) away from the Fermi level, leading to the reduction of CDW-gap magnitude and TCDW. This indicates a primary role of the SP density of states to stabilize CDW. The present result also suggests that the enhancement of superconductivity by Nb substitution is caused by the cooperation between the expansion of the Sb-derived electron pocket and the recovery of the V-derived density of states at the Fermi level.

6 pages, 3 figures

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• Surface-termination-dependent electronic states in kagome superconductors AV3Sb5 (A = K, Rb, Cs) studied by micro-ARPES
• Effects of Nb Doping on the Charge-Density Wave and Electronic Correlations in the Kagome Metal Cs(V${}_{1-x}$Nb${}_x$)${}_3$Sb${}_5$
• Pressure evolution of electron dynamics in the superconducting kagome metal CsV${}_3$Sb${}_5$
• Kagome metals
• Evolution of charge density waves from three-dimensional to quasi-two-dimensional in Kagome superconductors Cs(V${}_{1-x}{M}_x$)${}_3$Sb${}_5$ ($M$ = Nb, Ta)
• Glass-like Cross-plane Thermal Conductivity of Kagome Metals RbV3Sb5 and CsV3Sb5
• Dynamical decoding of the competition between charge density waves in a kagome superconductor
• Tuning electronic pairing by uniaxial strain in kagome lattices
• Photoemission Insights to Electronic Orders in Kagome Superconductor AV3Sb5
• The de Haas-van Alphen quantum oscillations in the kagome metal RbTi3Bi5
• Resistive anisotropy in the charge density wave phase of Kagome superconductor CsV3Sb5 thin films
• Evolution from three-dimensional charge density wave to one-dimensional stripe order in CsV${}_{3-x}$Ti${}_x$Sb${}_5$