Controllable phase transitions between multiple charge density waves in monolayer 1T-VSe2 via doping and strain engineering
Abstract
Two-dimensional (2D) materials are known to possess emergent properties that are not found in their bulk counterparts. Recent experiments have shown a 7 × 3 charge density wave (CDW) in monolayer 1T-VSe2, in contrast to the 4× 4× 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 and in-plane biaxial strain. With doping, the 7 × 3 CDW of the pristine VSe2 transfers to a 3 × 3 and 4× 4 phase, the latter of which is a projection of the bulk counterpart, at critical doping concentrations of around 0.2 holes per formula unit and 0.25 electrons per formula unit, respectively. The 4× 4 CDW phase can also be stabilized under compressive strain. Although electron-phonon coupling is prevailing in the CDW formation, we show that Fermi surface nesting is a good starting point to explain most of these transitions in monolayer 1T-VSe2. These results make VSe2 an appealing material for electronic devices based on controllable CDW phase transitions.