Gating monolayer WTe2 devices in nano ARPES

We investigate the effects of electrostatic doping on a 2D topological semimetal, monolayer WTe 2, employing nanometer-resolution angle-resolved photoemission spectroscopy (nano-ARPES). The exfoliated WTe 2 monolayer flake rests on an hBN flake and is capped by a monolayer of hBN to prevent oxidation and allow cleaning. During the photoemission measurements a gate voltage can be applied between a thin graphite electrode beneath the hBN and a graphene contact that overlaps the WTe 2 on top. The gate is observed to shift the Fermi energy by more than 100 meV, from valence to conduction band of monolayer WTe 2. The temperature and doping dependence of the spectrum yield insights into the nature of the bulk conductivity.