LAUSR

Using first-principles calculations, we identify the origin of the observed charge density wave (CDW) formation in a layered kagome metal CsV3Sb5. It is revealed that the structural distortion of kagome lattice forming the trimeric and hexameric V atoms is accompanied by the stabilization of quasimolecular states, which gives rise to the opening of CDW gaps for the V-derived multibands lying around the Fermi level. This Jahn-Tellerlike instability having the local lattice distortion and its derived quasimolecular states is a driving force of the CDW order. Specifically, the saddle points of multiple Dirac bands near the Fermi level, located at the M point, are hybridized to disappear along the kz direction, therefore not supporting the widely accepted Peierls-like electronic instability due to Fermi surface nesting. It is further demonstrated that applied hydrostatic pressure significantly reduces the interlayer spacing to destabilize the quasimolecular states, leading to a disappearance of the CDW phase at a pressure of ∼2 GPa. The presently proposed underlying mechanism of the CDW order in CsV3Sb5 can also be applicable to other isostructural kagome lattices such as KV3Sb5 and RbV3Sb5.