Figure 1.

Generation of AH currents. (a) Optical excitation creates spin alignment (S). The spins move (${\mathbf{v}}_{\mathrm{sf}}$) in the surface electric field. (b) A static in-plane magnetic field (B) induces Lamor precession and Hall rotation of S and ${\mathbf{v}}_{\mathrm{sf}}$, respectively. (c) The AH current along the direction $\mathbf{S}\times {\mathbf{v}}_{\mathrm{sf}}$ emits THz radiation which is detected with a sub-picosecond time resolution. It should be noted that the generation of AH currents cannot be accomplished for an out-of-plane magnetic field since in this case S and ${\mathbf{v}}_{\mathrm{sf}}$ are parallel to B and, consequently, no spin Hall angle between S and ${\mathbf{v}}_{\mathrm{sf}}$ will be formed.