Critical absorption of first sound near the smectic A-smectic C phase transition
Balandin V. A. , Gurovich E. V., Kashitsyn A. S., Pasechnik S. V., Shmelev O. Ya.
A new mechanism for the exciton-biexciton changes in the spectra of a semiconductor is proposed. This mechanism operates because of a direct virtual binding of two excitons to form a biexciton by virtue of their Coulomb interaction. It is shown that this mechanism determines the structural changes in spectra which have previously been linked with exclusively a "giant" oscillator strength of the exciton-biexciton transition. In particular, this new mechanism leads to an effective long-wavelength shift of exciton and biexciton levels.
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![](/ps/1112/article_16823_800_head.png "A new mechanism for the exciton-biexciton changes in the spectra of a semiconductor is proposed. This mechanism operates because of a direct virtual binding of two excitons to form a biexciton by virtue of their Coulomb interaction. It is shown that this mechanism determines the structural changes in spectra which have previously been linked with exclusively a "giant" oscillator strength of the exciton-biexciton transition. In particular, this new mechanism leads to an effective long-wavelength shift of exciton and biexciton levels.")