Enhanced Coupling of Superconductivity and Evolution of Gap Structure in CsV3Sb5 through Ta Doping

TL;DR

This study investigates how Ta doping in CsV3Sb5 kagome superconductors enhances superconductivity and alters the gap structure, showing increased Tc and a transition from anisotropic to isotropic s-wave gaps.

Contribution

It provides detailed specific heat measurements revealing the evolution of gap structure and coupling strength with Ta doping in CsV3Sb5.

Findings

Superconducting transition temperature increases from 2.8 K to 4.6 K with Ta doping.

Doped sample exhibits two isotropic s-wave gaps with a larger gap ratio of 5.04.

Suppression of charge density wave correlates with enhanced superconducting coupling.

Abstract

In this study, we present a detailed investigation of kagome superconductors CsV3Sb5 single crystal and its Ta-doped variant, Cs(V0.86Ta0.14)3Sb5, through specific heat measurements. Our results show a clear suppression of the charge density wave (CDW) and notable increase in the superconducting transition temperature (Tc) from 2.8 K to 4.6 K upon Ta doping. The electronic specific heat of the pristine CsV3Sb5 sample can be fitted with a model comprising an s-wave gap and a highly anisotropic extended s-wave gap, where the ratio 2{\Delta}/k_B T_c is smaller than the weak coupling limit of 3.5. For the doped sample Cs(V0.86Ta0.14)3Sb5, it exhibits two isotropic s-wave gaps, yielding the larger gap of 2{\Delta}/k_B T_c=5.04, which indicates a significant enhancement in superconducting coupling. This evolution is attributed to the increased density of states (DOS) near the Fermi level released through the suppression of the CDW gap. Our results demonstrate enhanced superconducting coupling and variation of gap structure in CsV3Sb5 due to Ta doping.