Origin of charge density wave in the layered kagome metal CsV3Sb5

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. We, thus, propose the Jahn-Teller-like instability having the local lattice distortion and its derived quasimolecular states as 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 k(z) 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 similar to 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.

Automated summary

Using first-principles calculations, the origin of the observed charge density wave (CDW) formation in a layered kagome metal CsV3Sb5 is identified. The structural distortion of the kagome lattice accompanies the stabilization of quasimolecular states, resulting in the opening of CDW gaps. Applied hydrostatic pressure destabilizes the quasimolecular states and leads to the disappearance of the CDW phase.