Photocurrent response in device-geometry engineered Anisotropic Van der Waals Metals

The geometry of mesoscopic devices, with dimensions comparable to the carrier mean free path, can significantly influence transport and optoelectronic responses. In this study, we explore the interplay of crystal anisotropy and device geometry in van der Waals semimetals. Using L-shaped devices fabricated from anisotropic van der Waals semimetals, we observe a robust zero-bias photocurrent when the laser is illuminated at the device corners, with its direction determined by the intrinsic anisotropy of the crystal. Zero bias photocurrent disappears in straight-channel structures, indicating that symmetry breaking originating from the synergetic effect of device geometry and crystal anisotropy is essential for this effect. Notably, the signal is significantly enhanced at low temperatures, far exceeding the values expected from resistance anisotropy alone. Our study reveals a novel mechanism for photocurrent generation and provides new design principles for directional optoelectronic devices based on intrinsic crystal anisotropy and device geometry.