Pressure-induced double-dome superconductivity in kagome metal CsTi3Bi5

We present high-pressure resistance measurements up to 40 GPa on recently discovered titanium-based kagome metal CsTi$_3$Bi$_5$. At ambient pressure, CsTi$_3$Bi$_5$ shows no evidence of superconductivity in resistivity and specific heat. By applying pressure, superconductivity emerges and the superconducting transition temperature ${\it T}_{\rm c}$ reaches its first maximum of 1.2 K at $\sim$5 GPa. Then the ${\it T}_{\rm c}$ is suppressed by pressure and cannot be detected around 10 GPa, manifesting as a superconducting dome. Remarkably, upon further increasing pressure above $\sim$13 GPa, another superconducting dome shows up, with the maximum ${\it T}_{\rm c}$ of 0.6 K and ending pressure at $\sim$36 GPa. The variation of ${\it T}_{\rm c}$ displays a clear double-dome shape in the superconducting phase diagram. Our work demonstrates the similarity between CsTi$_3$Bi$_5$ and CsV$_3$Sb$_5$, providing valuable insights into the rich physics of these novel kagome metals.