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HAIT Journal of Science and Engineering Volume 1, Issue 2, pp. 274-286 © 2004 Holon Academic Institute of Technology | ||||||
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On the theory of field induced relaxation in disordered systemAlexander L. Burin1, Yuri Kagan2, | ||||||
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1Department of Chemistry, Tulane University, New Orleans, LA 70118, USA 2RRC Kurchatov Institute, Moscow 123182, Russia *Corresponding author: iyp.iyp@g23.relcom.ru Received 6 November 2003, revised 25 January 2004, accepted 10 April 2004 | ||||||
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We investigate the relaxation of excitations in a strongly disordered ensemble of two-level-systems (TLS). A novel nonphonon mechanism destroying the Anderson localization in strong external fields is responsible for the relaxation. The TLS are supposed to interact via the dipole-dipole interaction that can be either of electrical or of elastic origin. An external field of low frequency and high amplitude coherently changing the TLS energy splitting is shown to control the relaxation. The case of adiabatic relaxation is considered. A concept of dressed excitation is introduced which allows us to simplify the analysis of relaxation phenomena. This concept is shown to lose meaning due to the spectral diffusion if the temperature is not low enough. In this case, the relaxation is treated in terms of initial TLS and is governed by the spectral diffusion. A crossover between these two regimes is revealed. In both cases the relaxation rates are surprisingly the same. The field and temperature dependencies of the excitation lifetime and the phase coherence time are found. The relation with the recent experimental data on ultra-low temperature relaxation in glasses is discussed and shown to support the results obtained. | ||||||
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___________________ Presented at Russian-Israeli Conference Frontiers in Condensed Matter Physics Shoresh, Israel, 19-24 October 2003 |