Electronic structure of Ga${}_{1-x}$Mn${}_x$As probed by four-wave mixing spectroscopy

Four-wave mixing experiments on GaMnAs indicate an increase in the optical response near the band gap with increasing Mn concentration. These findings are attributed to ($s$,$p$)-$d$ hybridization, which leads to an enhancement in the density of states in the valence band. Our experiments show that the nonlinearity of the four-wave mixing technique provides a highly sensitive probe for Mn-related changes in the electronic structure of GaMnAs.

Figure 1

Results of linear transmission experiments at 10 K. The laser spectrum for the 20-fs pulses used in the four-wave mixing experiments is indicated by the filled circles. (b) Schematic diagram of the four-wave mixing apparatus.

Figure 2

Results of spectrally-resolved four-wave mixing experiments at 10 K on the samples described in Table . The contour scale indicates the amplitude of the four-wave mixing signal, which is equal for all LT samples within the experimental uncertainty. The maximum contour scale for the two HT samples is much larger: by a factor of 20 for HT GaAs in (a) and by a factor of 12 for HT GaMnAs in (b).

Figure 3

(a) Four-wave mixing spectra at 10 K taken at zero pulse delay. (b) The laser excitation spectrum.