Nodal superconductivity and superconducting dome in the topological Kagome metal CsV3Sb5

Recently superconductivity was discovered in the Kagome metal $A$V$_3$Sb$_5$ ($A$ = K, Rb, and Cs), which has an ideal Kagome lattice of vanadium. These V-based superconductors also host charge density wave and topological nontrivial band structure. Here we report the ultralow-temperature thermal conductivity and high pressure resistance measurements on CsV$_3$Sb$_5$ with $T_c \approx$ 2.5 K, the highest among $A$V$_3$Sb$_5$. A finite residual linear term of thermal conductivity at zero magnetic field and its rapid increase in fields suggest nodal superconductivity. By applying pressure, the $T_c$ of CsV$_3$Sb$_5$ increases first, then decreases, showing a clear superconducting dome. Both nodal superconductivity and superconducting dome point to unconventional superconductivity in this V-based superconductor, which could be chiral $d$-wave or odd-parity pairing superconducting state.