Semimetal Td‐WTe2 demonstrates broadband anomalous and polarization‐sensitive photoresponse. The giant photocurrent and responsivity reach 40 µA and 250 A W−1 for a 3.8 µm laser at 77 K, and the photocurrent anisotropic ratio of 4.9 for a 514.5 nm laser. Consistently, first‐principles calculations confirm angle sensitive bandgap opening of WTe2 by polarized light, showing its photodetection potential. Abstract Recently, an emergent layered material Td‐WTe2 was explored for its novel electron–hole overlapping band structure and anisotropic inplane crystal structure. Here, the photoresponse of mechanically exfoliated WTe2 flakes is investigated. A large anomalous current decrease for visible (514.5 nm), and mid‐ and far‐infrared (3.8 and 10.6 µm) laser irradiation is observed, which can be attributed to light‐induced surface bandgap opening from the first‐principles calculations. The photocurrent and responsivity can be as large as 40 µA and 250 A W−1 for a 3.8 µm laser at 77 K. Furthermore, the WTe2 anomalous photocurrent matches its in‐plane crystal structure and exhibits light polarization dependence, maximal for linear laser polarization along the W atom chain a direction and minimal for the perpendicular b direction, with the anisotropic ratio of 4.9. Consistently, first‐principles calculations confirm the angle‐dependent bandgap opening of WTe2 under polarized light irradiation. The anomalous and polarization‐sensitive photoresponses suggest that linearly polarized light can significantly tune the WTe2 surface electronic structure, providing a potential approach to detect polarized and broadband lights up to far infrared range.

Published in: "Advanced Materials".