Charge density wave and pressure-dependent superconductivity in the kagome metal CsV3Sb5 : A first-principles study

The kagome metals $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ ($A=\mathrm{K}$, Rb, and Cs) have received intensive research interest due to the presence of charge density waves (CDWs), ${\mathbb{Z}}_{2}$ topological surface states, and intriguing pressure-dependent superconductivity. Using first-principles calculations, here we study the origin of the CDW order in ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ and its superconducting properties under pressure up to 45 GPa. We reveal that the momentum-dependent electron-phonon coupling (EPC) effect plays an important role in the formation of the CDW order. Upon compression, the movement of the van Hove singularity, which induces the change in the density of states at the Fermi level, as well as the redistribution of the EPC, can explain the experimentally observed double superconducting domes. The main contribution to the EPC is varied from in-plane vibrational modes in superconducting area I (2--15 GPa) to out-of-plane modes in superconducting area II (15--45 GPa). Our observations clarify the origin of the CDW order and shed some light on understanding the experimental observations of pressure-dependent superconductivity in ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$.