Tuning the Decay Length of Long-Range Photocurrent in Weyl Semimetals by Engineering the Weighting Field

In conventional materials, symmetry breaking induced by spatial inhomogeneities typically confines self-powered photocurrents to edges, corners, or interfaces. In this work, we observe long-range photocurrents with multidomain patterns extending from the contacts into the interior of homogeneous Weyl semimetals (WTe₂ and TaIrTe₄) at room temperature. It is revealed that the long-range photocurrent is approximately proportional to the anisotropic divergence of the weighting field ((σS∇)·E). By increasing the conductivity anisotropy or enlarging the angle between the material's a-axis and the channel direction, the gradient of (σS∇)·E along the a-axis is reduced, and the decay length of the long-range photocurrent (L_d) is substantially increased. As a result, a large L_d of up to 20.5 μm is achieved in a TaIrTe₄ device with the a-axis oriented perpendicular to the channel direction, far exceeding typical photocurrent decay lengths observed in conventional low-dimensional materials.