Self-consistent driven Bloch oscillations in excitonic Wannier-Stark ladder
Master of Science
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In this thesis, we present a theoretical model of Self-consistent driven Bloch oscillations (SCD BO) of different types of charge carriers in biased semiconductor superlattices photoexcited via ultra-short near-bandgap optical pulses. In this work, we wish to assess the influence of the unbound continuum excitonic states on the Is excitons. This is modelled by calculating the full dynamics of Is excitons and free electron-hole pairs, including the Coulomb interaction in a mean-field approximation. All the calculations are based on a recently-developed Quasibosonic treatment, by which we can study SCD BO to infinite order in optical field without loosing the crucial intraexcitonic electron-hole correlations. T he interaction of Is excitons with free electron-hole pairs is studied in both coherent and non-coherent systems. The numerical results obtained are found to be partially in agreement with the experimental results reported by F. Loser et al. [ Phys. Rev. Lett. 85, 4763 (2000) ]. However, we find several serious discrepancies that indicate that a more complete treatment may have to be adopted in future work. Despite this, the work in this thesis provides some useful insights to the coherent response of photoexcited semiconductor superlattices, and lays the ground work for fu tu re study.