Controllable phase transitions between multiple charge density waves in monolayer 1T-VSe2 via charge doping

Two-dimensional materials are known to possess emergent properties that are not found in their bulk counterparts. Recent experiments have shown a 7 x 3 charge density wave (CDW) in monolayer 1 T-VSe2, in contrast to the 4 x 4 x 3 phase in bulk. Here, via first-principles calculations, we show that multiple CDW phases compete in monolayer VSe2, the ground state of which can be tuned by charge doping. With doping, the 7 x 3 CDW of the pristine VSe2 transfers to a 4 x 4 or 3 x 3 phase, at critical doping concentrations of around 0.2 electrons per formula unit and 0.2 holes per formula unit, respectively. These transitions are further understood by analyzing the role of Fermi surface nesting and momentum-dependent electron-phonon coupling in monolayer 1T-VSe2. These results make VSe2 an appealing material for electronic devices based on controllable CDW phase transitions.