Electronic structure and charge injection across transition metal dichalcogenide heterojunctions: theory and experiment.

We combine {\em ab initio} density functional electronic structure calculations for an NbSe$_2$/WSe$_2$ bilayer with quantum transport measurements of the corresponding heterojunction between a few-layer WSe$_2$ semiconductor and a metallic NbSe$_2$ layer. Our theoretical results suggest that, besides a rigid band shift associated with charge transfer, the presence of NbSe$_2$ does not modify the electronic structure of WSe$_2$. Since the two transition metal dichalcogenides are structurally similar and display only a small lattice mismatch, their heterojunction can efficiently transfer charge across the interface. These findings are supported by transport measurements for WSe$_2$ field-effect transistors with NbSe$_2$ contacts, which exhibit nearly ohmic behavior and phonon-limited mobility in the hole channel, indicating that the contacts to WSe$_2$ are highly transparent.