Physical review. B, Condensed matter
Polarization dependence of beating phenomena at the energetically lowest exciton transition in GaAs quantum wells
E. J. Mayer, G. O. Smith, V. Heuckeroth, J. Kühl, K. Bott, A. Schulze, T. Meier, Stefan W. Koch, P. Thomas, R. Hey, Klaus Ploog
Abstract
We report time-resolved degenerate four-wave-mixing experiments on a high-quality single GaAs quantum well. The signals for parallel and cross-polarized exciting pulses show pronounced quantum beats with different frequencies corresponding to the heavy/light-hole splitting and the biexciton binding energy, respectively. Comparison of the experimental data with solutions of the optical Bloch equations for a phenomenological model system shows that these features result from strong contributions of the biexcitonic state. The importance of biexcitons to the nonlinear coherent response of the two-dimension exciton is further confirmed by the frequency dependence of the time-integrated four-wave-mixing signal amplitudes measured for the two polarization geometries.