Magneto-Optical Detection of the Orbital Hall Effect in Chromium

The orbital Hall effect has been theoretically predicted but its direct observation is a challenge. Here, we report magneto-optical detection of current-induced orbital accumulation at the surface of a light 3d transition metal Cr. The orbital polarization is in-plane, transverse to the current direction, and scales linearly with current density, consistent with the orbital Hall effect. Comparing the experimental results with ab initio calculations, we determine the orbital Hall angle in a single layer Cr film. From thickness-dependent measurements, we estimate the characteristic length of the orbital transport.