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Measurement of spin-flip scattering and photon echo response in GaMnAs

Four-wave mixing techniques are applied to Ga1-xMnxAs, providing new insight into the fundamental properties of the III-Mn-V semiconductors. Clear signatures of (s,p)-d hybridization associated with the MnGa substitutional impurity are observed in the spectrum of the four-wave mixing signal. Experiments on a ferromagnetic sample show no evidence of hole occupation in the valence band for x = 5%. A photon echo is observed on the interband transition, despite the strong exchange coupling and large defect density in this system. Rapid dephasing associated with Mn-hole spin-flip scattering is observed, with a measured upper bound on the spin-flip scattering time of 40 fs. An excitonic signature tied to many-body effects is observed in LT-GaAs.