Evidence of charge density wave with anisotropic gap in a monolayer VTe2 film

Angle-resolved photoemission spectroscopy measurements reveal the evidence of a charge density wave (CDW) and the underlying mechanism in a monolayer VTe${}_{2}$ film. The Fermi surface map is partially gapped and shows an arc shape. The CDW gap is found to be rather anisotropic and attributed to the imperfect nesting. First-principles calculations further indicate electron-phonon coupling at the corresponding wave vector. These observations suggest that both Fermi surface nesting and phonon instability contribute significantly to the CDW formation in this monolayer VTe${}_{2}$ film.