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Lorenz number in high Tc superconductors: evidence for bipolarons

K. K. Lee·A. S. Alexandrov·W. Y. Liang
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Abstract

Strong electron-phonon interaction in cuprates has gathered support over the last decade in a number of experiments. While phonons remain almost unrenormalised, electrons are transformed into itinerent bipolarons and thermally excited polarons when the electron-phonon interaction is strong. We calculate the Lorenz number of the system to show that the Wiedemann-Franz law breaks down because of the interference of polaron and bipolaron contributions in the heat flow. The model fits numerically the experimental Hall Lorenz number, which provides a direct evidence for bipolarons in the cuprates.

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K. K. Lee, A. S. Alexandrov, W. Y. Liang. 2002-11-28. Lorenz number in high Tc superconductors: evidence for bipolarons. https://doi.org/10.1103/physrevlett.90.217001

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