Signature of inverse orbital Hall effect in silicon studied using time-resolved terahertz polarimetry

We investigated the anomalous Hall conductivity induced in silicon by circularly polarized light at room temperature using near-infrared (NIR) pump-terahertz (THz) probe spectroscopy. The time-resolved detection scheme eliminates the large nonlinear current generated by the field-induced circular photogalvanic effect, allowing exclusive observation of a long-lived anomalous Hall conductivity of photocarriers that depends on the helicity of NIR light. The magnitude of this conductivity is comparable to that of GaAs despite silicon’s much weaker spin-orbit coupling, and its robustness against NIR photon energy rules out a spin-polarization-based origin, which occurs only in the vicinity of the bandgap. These results suggest the emergence of the inverse orbital Hall effect, paving the way for silicon-based orbitronics.