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

We report experimental evidence of charge density wave (CDW) transition in monolayer 1T-VTe₂ film. Low energy electron diffraction (LEED) measurements reveal 4×4 reconstruction peaks below transition temperature. Angle-resolved photoemission spectroscopy (ARPES) measurements reveal arc-like pockets with anisotropic CDW gaps up to 50 meV. The anisotropic CDW gap is attributed to the imperfect nesting of the CDW wave vector, and first-principles calculations reveal phonon softening at the same vector. These results suggest the important roles of both Fermi surface nesting and electron-phonon interaction in the CDW mechanism of monolayer VTe₂ film.