Accuracy of second order perturbation theory in the polaron and variational polaron frames
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Cao_Accuracy of second.pdf
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1.46 MB
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Author(s)
Lee, Chee Kong
Moix, Jeremy
Cao, Jianshu
Date Issued
May 2012
Journal
The Journal of Chemical Physics
Publisher
American Institute of Physics (AIP)
Citation
Lee, Chee Kong, Jeremy Moix, and Jianshu Cao. “Accuracy of second order perturbation theory in the polaron and variational polaron frames.” The Journal of Chemical Physics 136, no. 20 (2012): 204120. © 2012 American Institute of Physics
Version
Final published version
Abstract
In the study of open quantum systems, the polarontransformation has recently attracted a renewed interest as it offers the possibility to explore the strong system-bath coupling regime. Despite this interest, a clear and unambiguous analysis of the regimes of validity of the polarontransformation is still lacking. Here we provide such a benchmark, comparing second order perturbation theory results in the original untransformed frame, the polaron frame, and the variational extension with numerically exact path integral calculations of the equilibrium reduced density matrix. Equilibrium quantities allow a direct comparison of the three methods without invoking any further approximations as is usually required in deriving master equations. It is found that the second order results in the original frame are accurate for weak system-bath coupling; the results deteriorate when the bath cut-off frequency decreases. The full polaron results are accurate for the entire range of coupling for a fast bath but only in the strong coupling regime for a slow bath. The variational method is capable of interpolating between these two methods and is valid over a much broader range of parameters.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1063/1.4722336
