  We induce ultrafast magneto-photocurrents in a GaAs crystal employing
interband excitation with femtosecond laser pulses at room temperature and
non-invasively separate surface and bulk contributions to the overall current
response. The separation between the different symmetry contributions is
achieved by measuring the simultaneously emitted terahertz radiation for
different sample orientations. Excitation intensity and photon energy
dependences of the magneto-photocurrents for linearly and circularly polarized
excitations reveal an involvement of different microscopic origins, one of
which we believe is the inverse Spin-Hall effect. Our experiments are important
for a better understanding of the complex momentum-space carrier dynamics in
magnetic fields.
