Pressure-tuning topological phase transitions in Kagome superconductor CsTi${}_3$Bi${}_5$

Abstract

Recently, the Kagome metal CsTi${}_3$Bi${}_5$ has exhibited several novel quantum properties similar to CsV${}_3$Sb${}_5$, such as nontrivial topology, double-dome superconductivity, and flat band features. However, CsTi${}_3$Bi${}_5$ lacks the charge-density wave (CDW) present in CsV${}_3$Sb${}_5$, making the study of its emergence of double-dome superconductivity a focus of research. In this work, we have identified an order parameter, the three-band Z${}_2$ topological index, that can describe the superconducting phase diagram of CsTi${}_3$Bi${}_5$ under pressure. Its evolution with pressure follows the expected behavior for superconductivity. Furthermore, the results of the Fermi surface under pressure reveal the potential presence of a Lifshitz transition in the vicinity of the vanishing point of the superconducting temperature change with pressure in CsTi${}_3$Bi${}_5$. These results indicate that the superconducting behavior of CsTi${}_3$Bi${}_5$ under pressure is caused by changes in the electronic structure leading to alterations in the topological properties, provide new insights and approaches for understanding the superconducting phenomenon in Kagome metals.