Structural and electronic phase transitions of MoTe₂ induced by Li ionic gating

Monolayer MoTe₂ has semiconducting and semimetallic phases with small energy difference, and the relative stability is readily reversed by gating. By first-principles calculations, we investigate the changes in atomic structure, electronic structure, and relative stability of two phases induced by Li ionic gating. To model Li ionic gating, we employ two approaches; one is direct adsorption of Li on MoTe₂ and the other is introducing non-contacting Li plate over MoTe₂. We show phonon instability in H -phase of MoTe₂ with increasing the amount of charge transfer from Li, which implies a large electron-phonon coupling in the system resulting in a charge density wave state. Structural distortion is also observed in highly doped T _d phase. The transition energy barrier from distorted H phase to distorted T _d phase is reduced considerably compared to that of pristine MoTe₂. (paper)