UBC Theses and Dissertations
Some higher-order processes in the optical absorption and emission by impurities in nonmetals Chow, Hau-Cheung
The effects arising from quadratic electron-phonon interaction and anharmonicity on the optical spectra of imperfections in nonmetals are examined. The absorption or emission line-shape function is expressed in terms of Kubo's formula and is reduced to a trace over phonon states only via the application of the Barrie-Sharpe method. This trace is evaluated with the aid of quantum field-theoretic techniques. It is shown that both the quadratic electron-phonon interaction and anharmonicity modify the phonon spectrum, and the influence of this modification on the optical spectra is studied in detail with regard to position, intensity, width, Stokes' shift and mirror reflection symmetry.
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