Copyright The American Physical Society 1999. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed or modified without the express permission of The American Physical Society. The archivial version of this work was published in Phys. Rev. B 60(1), 299-307 (July 1, 1999).

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Mobility of an electron
in a multimode polar lattice

Robert W. Hellwarth

University of Southern California
Departments of Physics and Electrical Engineering
Los Angeles
CA 90089-0484

Ivan Biaggio

Nonlinear Optics Laboratory, Institute of Quantum Electronics,
Swiss Federal Institute of Technology, ETH-Hönggerberg,
CH-8093 Zürich, Switzerland

(Received 12 November 1998)


The interaction of a free electron with a polar lattice possessing more than one infrared-active optical-phonon mode is considered. From the full Lagrangian describing the electron-lattice system in the presence of an applied field we derive an effective electron-phonon coupling constant and an effective longitudinal optical-phonon frequency that we argue give accurate predictions when used in the extensive, existing polaron theo-ries. We apply this formalism to the strongly coupled large polaron of Bi12SiO20 , where the Boltzmann equation cannot apply. We calculate a theoretical prediction for the large polaron mobility as a function of temperature which gives good agreement with experiment. We determine the temperature dependence of Feynman's variational parameters v and w to assist in our predictions.