Figure 1

Generation of AH currents. (a) Optical excitation creates spin alignment (S). The spins move (\({{\bf{v}}}_{{\rm{sf}}}\)) in the surface electric field. (b) A static in-plane magnetic field (B) induces Lamor precession and Hall rotation of S and \({{\bf{v}}}_{{\rm{sf}}}\), respectively. (c) The AH current along the direction \({\bf{S}}\times {{\bf{v}}}_{{\rm{sf}}}\) 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 \({{\bf{v}}}_{{\rm{sf}}}\) are parallel to B and, consequently, no spin Hall angle between S and \({{\bf{v}}}_{{\rm{sf}}}\) will be formed.