Photoresponse of a Dirac-Weyl interface composed of graphene and WTe₂

Although Graphene and WTe₂ are both atomically thin semimetals whose density of states diminishes at the charge neutrality point, each exhibit highly distinct band topologies in their low energy electronic structure. While graphene hosts Dirac-like excitations with highly symmetric electron and hole bands, WTe₂ has been shown to be a type II Weyl semimetal with compensated electron-hole pockets. Photoexcitation combined with electronic magneto-transport provides a deep understanding of the dynamics that govern electrical and optical conductivities and give us an opportunity to explore the consequences of unusual band topologies at a Dirac-Weyl interface. Here, we use scanning photocurrent microscopy to study the local photoresponse at a van der Waals heterojunction of WTe2 and Graphene. We examine the semimetal-semimetal interface response as a function of interlayer voltage, local gate voltage, laser power, wavelength, and magnetic field, finding highly sensitive photoresponsivity attributed to a photo-thermoelectric effect. Our measurements establish the groundwork for low temperature studies into the origins of this unusual photoresponse and give important insights into the design and development of unique magneto-optoelectronic sensors based on WTe₂.