Pressure-tuning topological phase transitions in Kagome superconductor CsTi₃Bi₅

Recently, the Kagome metal CsTi₃Bi₅ has exhibited several novel quantum properties similar to CsV₃Sb₅, such as nontrivial topology, double-dome superconductivity, and flat band features. However, CsTi₃Bi₅ lacks the charge-density wave (CDW) present in CsV₃Sb₅, 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 Z₂ topological index, that can describe the superconducting phase diagram of CsTi₃Bi₅ 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 CsTi₃Bi₅. These results indicate that the superconducting behavior of CsTi₃Bi₅ 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.