Superconducting, Topological, and Transport Properties of Kagome Metals CsTi 3 Bi 5 and RbTi 3 Bi 5

Abstract

The recently discovered ATi 3 Bi 5 (A=Cs, Rb) exhibit intriguing quantum phenomena including superconductivity, electronic nematicity, and abundant topological states. ATi 3 Bi 5 present promising platforms for studying kagome superconductivity, band topology, and charge orders in parallel with AV 3 Sb 5 . In this work, we comprehensively analyze various properties of ATi 3 Bi 5 covering superconductivity under pressure and doping, band topology under pressure, thermal conductivity, heat capacity, electrical resistance, and spin Hall conductivity (SHC) using first-principles calculations. Calculated superconducting transition temperature ( T c ) of CsTi 3 Bi 5 and RbTi 3 Bi 5 at ambient pressure are about 1.85 and 1.92 K. When subject to pressure, T c of CsTi 3 Bi 5 exhibits a special valley and dome shape, which arises from quasi-two-dimensional compression to three-dimensional isotropic compression within the context of an overall decreasing trend. Furthermore, T c of RbTi 3 Bi 5 can be effectively enhanced up to 3.09 K by tuning the kagome van Hove singularities (VHSs) and flat band through doping. Pressures can also induce abundant topological surface states at the Fermi energy ( E F ) and tune VHSs across E F . Additionally, our transport calculations are in excellent agreement with recent experiments, confirming the absence of charge density wave. Notably, SHC of CsTi 3 Bi 5 can reach up to 226 ℏ ·(e· Ω ·cm) –1 at E F . Our work provides a timely and detailed analysis of the rich physical properties for ATi 3 Bi 5 , offering valuable insights for further experimental verifications and investigations in this field.