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Phonon Thermodynamics versus Electron-Phonon Models

Marco Zoli
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Abstract

Applying the path integral formalism we study the equilibrium thermodynamics of the phonon field both in the Holstein and in the Su-Schrieffer-Heeger models. The anharmonic cumulant series, dependent on the peculiar source currents of the {\it e-ph} models, have been computed versus temperature in the case of a low energy oscillator. The cutoff in the series expansion has been determined, in the low $T$ limit, using the constraint of the third law of thermodynamics. In the Holstein model, the free energy derivatives do not show any contribution ascribable to {\it e-ph} anharmonic effect. We find signatures of large {\it e-ph} anharmonicities in the Su-Schrieffer-Heeger model mainly visible in the temperature dependent peak displayed by the phonon heat capacity.

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BibTeXRIS

Marco Zoli. 2004-11-17. Phonon Thermodynamics versus Electron-Phonon Models. https://doi.org/10.1103/physrevb.70.184301

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