Anomalous photo-thermoelectric transport due to anisotropic energy dispersion in WTe2

Band structures are vital in determining the electronic properties of materials. Recently, the two-dimensional (2D) semimetallic transition metal tellurides (WTe2 and MoTe2) have sparked broad research interest because of their elliptical or open Fermi surface, making it distinct from the conventional 2D materials. In this study, we demonstrate a centrosymmetric photo-thermoelectric voltage distribution in WTe2 nanoflakes, which has not been observed in common 2D materials such as graphene and MoS2. Our theoretical model shows the anomalous photo-thermoelectric effect arises from an anisotropic energy dispersion and micrometre-scale hot carriers diffusion length of WTe2. Further, our results are more consistent with the anisotropic tilt direction of energy dispersion being aligned to the b axis rather than a axis of the WTe2 crystal, which is consistent with the previous first-principle calculations as well as magneto-transport experiments. Our work shows the photo-thermoelectric current is strongly confi...