Tunable charge density wave phases in transition metal dichalcogenides heterostructures

Transition metal dichalcogenides are famed as functional materials harboring a rich variety of charge density wave (CDW) distortions. Recent experiments indicate the degeneration of CDW phases in transition metal dichalcogenides on various substrates. Here we show by comprehensive first-principles calculations that the CDW phases at the interface of $1T\text{\ensuremath{-}}{\mathrm{TiSe}}_{2}/2H\text{\ensuremath{-}}{\mathrm{NbSe}}_{2}$ heterostructures are tunable. In the heterostructures, the CDW phase is inhibited in ${\mathrm{TiSe}}_{2}$ layers while retained in ${\mathrm{NbSe}}_{2}$ layers. The collapse of CDW in ${\mathrm{TiSe}}_{2}$ is caused by the interface work function difference and the induced charge transfer, and confined to the first two ${\mathrm{TiSe}}_{2}$ layers closest to the interface. This interface effect is maintained even when an external electric field is applied to balance the difference in work function, but biaxial tensile strain can effectively restore the CDW phase in the ${\mathrm{TiSe}}_{2}$ layer. As for ${\mathrm{NbSe}}_{2}$, since the half-filled Nb-d orbitals are the only electronic states around the Fermi level, substrate effect can hardly affect the CDW in it. Our study paves the way for manipulating phase transitions of transition metal dichalcogenides via van der Waals interface engineering.