Reversing EFISH: Spin-Induced Static Electric Fields in Symmetry-Broken Plasmonic Nanostructures

Generating localized DC potentials without intrusive contacts remains a fundamental challenge in optoelectronics and hot-carrier catalysis. Here, we theoretically demonstrate the all-optical generation of a static electric field within a single gold L-shaped nanoantenna. By exploiting the spectral overlap between orthogonal dipolar and quadrupolar plasmonic modes, we engineer a symmetry-breaking mechanism that rectifies optical oscillations into a directed electron flow. Hydrodynamic simulations reveal that the phase-coupling of these modes locally sorts optical spin angular momentum, driving second-order drift currents throughout the structure. This creates a stable charge separation with switchable polarity, yielding a localized static electric field estimated at 78.4 V·m^-1 under an excitation intensity of 10¹⁰ W·cm^-2. Crucially, the field's direction is deterministically controlled by the incident light's helicity. These findings provide a physical blueprint for "batteryless" nanocircuits, opening new avenues for spatially resolved photocatalysis and ultrafast optoelectronic modulation.