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Urbach's Rule and Phase Fluctuations of the Transmitted Light
Author(s) -
Skettrup T.
Publication year - 1981
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.2221030219
Subject(s) - exciton , phonon , coherence (philosophical gambling strategy) , condensed matter physics , phase (matter) , physics , absorption (acoustics) , resonance (particle physics) , thermal fluctuations , thermal , optics , molecular physics , atomic physics , quantum mechanics , thermodynamics
It is shown that both Urbach's rule (exponentially increasing absorption edge) and the large fluctuations of the phase of transmitted light observed in depolarization experiments can be derived from the same phenomenon, namely the fluctuating exciton resonance energy caused by the fluctuations in the phonon number in thermal equilibrium. A simple layer model is applied in order to derive quantitative results for absorption and phase fluctuation. The comparison of these results with experimental values for ZnO yields a good agreement. A coherence length of the LO phonons interacting with excitons is also obtained.