Nonlinear phenomena in condensed matter physics have been explored extensively in exotic materials, including materials with broken inversion symmetry, topological materials, metamaterials, and quantum wells. However, conventional nonmagnetic transition metals have largely been overlooked in this context because of their perceived relative simplicity. Here, we reveal the unexplored potential of nonmagnetic single-element metals by focusing on one type of nonlinear phenomenon: photocurrent generation induced by spin accumulation due to the spin Hall effect at the material edges. Distinctive behavior at the material edges, where the spatial symmetry is intrinsically broken, leads to observation of the nonlinear phenomenon. The resulting photocurrent is identified as a linear injection current and is associated with both time-reversal symmetry breaking and space-inversion symmetry breaking. This observation challenges the prevailing notion that nonlinear phenomena are exclusively observed in more exotic materials. We perform scanning photovoltage microscopy on Pt, W, Cu, and perpendicular magnetic anisotropy films to verify and characterize the observed linear injection current experimentally, thus confirming the crucial roles of spin accumulation and edge asymmetry in photocurrent generation. This finding provides a comprehensive understanding of linear injection currents realized during symmetry violation and is promising for development of spin- and symmetry-based techniques.

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• Photocurrent
• Spin accumulation
• Spin current
• Spin polarization