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X(5) signature in th four-wave-mixing signal from a GaAs/Al(0.3)Ga(0.7)As superlattice
X/5 Vorzeichen beim Vierwellen-Mischen Signal eines GaAs/Al(0.3)Ga(0.7)As Übergitters
We analyze coherent beats with a period corresponding to the biexciton binding energy in time-integrated four-wave-mixing experiments in a GaAs/Al0.3Ga0.7As superlattice at high excitation densities. Theoretical and experimental evidence is presented that the beating in the decay is a fifth-order process in the electric field, and therefore Chi(5) contributions to the four-wave-mixing signal in the 2 k2 - k1 direction have to be considered for a qualitative interpretation of the measured data. In order to model the experiment we use a microscopic dynamic density-matrix theory in a real-space representation.