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Optical Excitation and Bose Condensation of Excitons in Low‐Dimensional Systems
Author(s) -
Glutsch S.,
Bechstedt F.,
Zimmermann R.
Publication year - 1992
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221720131
Subject(s) - exciton , physics , bloch equations , biexciton , condensed matter physics , coulomb , condensation , excitation , master equation , quantum mechanics , electron , atomic physics , quantum , thermodynamics
The linear optical response of excitons is studied in low‐dimensional semiconductor systems – bulk, quantum well, quantum wire – pumped near the energy of the lowest exciton transition under inclusion of many‐body interactions. Attention is focused especially to three aspects: (i) influence of dimensionality on the Coulomb interaction, (ii) different behaviour of the optical response for pump frequencies lower than or close to the nominal exciton resonance, and (iii) time dependence until reaching stationarity. For this purpose the two‐band Bloch equations and the generalized gap equations are simultaneously solved. Far from the absorption edge results for the excitonic dynamical Stark effect are confirmed, at least in the collision‐free limit. For pump frequencies near or above the nominal exciton resonance an additional stationary solution of the gap equation is observed that is not vanishing for zero pump field and, therefore, characterizes a Bose‐like condensation in the electron–hole system. In the fully time‐dependent regime it is studied how this so‐called “excitonic insulator” can be reached during the time evolution. The resulting optical spectra as well as the existence and observability of the condensed phase are discussed.