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Quantum coherence of continuum states in the valence band of GaAs quantum wells

Quantenkohärenz von Zuständen im Kontinuum im Valenzband von GaAs quantum wells


Physical review letters 77 (1996), No.14, pp.3045-3048
ISSN: 0031-9007
Journal Article
Fraunhofer IAF ()
heterostructure; Heterostruktur; III-V Halbleiter; III-V semiconductors; time resolved measurement; zeitaufgelöste Messung

Quantum beats of heavy and light holes in GaAs quantum wells are investigated in femtosecond time-resolved four-wave mixing and transmission experiments as a function of optical excitation energy. Under nonexcitonic excitation conditions, the four-wave mixing signal disappears due to the immediate loss of the interband coherence of continuum states. In the transmission experiment, the quantum beats are observed up to excess energies of 75 meV above the exciton resonances. The experimental data clearly demonstrate the coherence of continuum states in the valence band. Changes of the beat frequency with the excitation energy are due to the dispersion of the valence bands.