Room-Temperature Geometrical Circular Photocurrent in Few-Layer MoS 2 .

Valleytronics, i.e., the manipulation of the valley degree of freedom, offers a promising path for energy-efficient electronics. One of the key milestones in this field is the room-temperature manipulation of the valley information in thick-layered material. Using scanning photocurrent microscopy, we achieve this milestone by observing a geometrically dependent circular photocurrent in a few-layer molybdenum disulfide (MoS ₂ ) under normal incidence. Such an observation shows that the system symmetry is lower than that of bulk MoS ₂ material, preserving the optical chirality-valley correspondence. Moreover, the circular photocurrent polarity can be reversed by applying electrical bias. We propose a model where the observed photocurrent results from the symmetry breaking and the built-in field at the electrode-sample interface. Our results show that the valley information is still retained even in thick-layered MoS ₂ at room temperature and opens up new opportunities for exploiting the valley index through interface engineering in multilayer valleytronics devices.