Pressure-induced Double-dome Superconductivity in Kagome Metals ATi₃Bi₅ (A = Cs, Rb)

The recently discovered titanium-based kagome metal ATi₃Bi₅ (A = Cs, Rb) provides a new platform to explore novel quantum phenomena. In this work, the transport properties of ATi₃Bi₅ (A = Cs, Rb) are systematically investigated under high pressure. Although ATi₃Bi₅ (A = Cs, Rb) shows no evidence of superconductivity at ambient pressure, the pressure-induced double-dome superconductivity is observed in both compounds, resembling the superconducting phase diagram of AV₃Sb₅ (A = Cs, Rb and K) under pressure. High-pressure X-ray diffraction measurements exclude the pressure-induced structural phase transition. A slope change in the c/a ratio was found between 12.4 and 14.9 GPa, indicating the occurrence of lattice distortion. The distinct changes of electronic band structure revealed by first-principles calculations further explain the emergence of superconductivity in the two domes. These findings suggest that pressure can effectively tune the electronic properties of ATi₃Bi₅, providing new insights into the rich physics of kagome metals.