Coherent Oscillations of a Wave Packet in a Semiconductor Double Quantum-Well Structure,
AT AND T BELL LABS HOLMDEL NJ
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We present the first observation of the spatial dynamics of a wavepacket in a solid. Using an ultrashort laser pulse, we create an excitonic wavepacket in one well of an asymmetric double quantum well structure. The oscillation of this wavepacket from one well to another and back is traced by time-resolved pump-probe spectroscopy as well as time-resolved degenerate four-wave-mixing. We present results for two GaAsAlGaAs double quantum wells with oscillation periods of about 1.3ps and 8OOfs, respectively. The experimental observations are compared with a theory that shows that the two experimental techniques give complementary information about the relaxation dynamics of the coupled system. The analysis of the experiment explains the strong damping of the oscillations by the fast thermalization between the delocalized states.
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