Origin of Charge Density Wave in Layered Kagome Metal CsV3Sb5
일 시 : 2021년 09월 16일 목요일 16:00
연 사 : 조 준 형 교수 (한양대학교 물리학과)
장 소 : 온라인 진행 (https://us02web.zoom.us/j/81101834598?pwd=RkZIdXJLL1lOWXBjamc2Ylg3VUtRZz09)
초 록
Using first-principles calculations, we identify the origin of the observed charge density wave (CDW) forma- tion 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-Teller- like instability having an interplay between 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 RbV3 Sb5.