Experimental Observation of the Inverse Spin Hall Effect at Room Temperature

We observe the inverse spin Hall effect in a two-dimensional electron gasconfined in AlGaAs/InGaAs quantum wells. Specifically, we find that aninhomogeneous spin density induced by the optical injection gives rise anelectric current transverse to both the spin polarization and its gradient. Thespin Hall conductivity can be inferred from such a measurement through theEinstein relation and the Onsager relation, and is found to have the order ofmagnitude of $0.5(e^{2}/h)$. The observation is made at the room temperatureand in samples with macroscopic sizes, suggesting that the inverse spin Halleffect is a robust macroscopic transport phenomenon.