Unusual competition of superconductivity and charge-density-wave state in a compressed topological kagome metal

Abstract Understanding the competition between superconductivity and other ordered states (such as antiferromagnetic or charge-density-wave (CDW) state) is a central issue in condensed matter physics. The recently discovered layered kagome metal AV3Sb5 (A = K, Rb, and Cs) provides us a new playground to study the interplay of superconductivity and CDW state by involving nontrivial topology of band structures. Here, we present high-pressure electrical transport measurements for CsV3Sb5 with the highest Tc of 2.7 K in AV3Sb5 family. The CDW transition is monotonically suppressed by pressure, while superconductivity is enhanced with increasing pressure up to P1 ≈0.7 GPa, then an unexpected suppression on superconductivity happens until pressure around 1.2 GPa. The CDW is completely suppressed at a critical pressure P2≈2 GPa together with a maximum Tc of about 8 K. In contrast to a common dome-like behavior, the pressure-dependent Tc shows an unexpected double-peak behavior. The unusual suppression of Tc at P1 is linked to a Lifshitz transition of Fermi surface evidenced by quantum oscillation experiment, a sudden enhancement of the residual resistivity and a rapid decrease of magnetoresistance. A possible nearly commensurate CDW state involving the formation of CDW domain wall has been used to account for the Lifshitz transition. Our discoveries indicate an unusual competition between superconductivity and CDW state in pressurized kagome lattice.