Lorenz number in high Tc superconductors: evidence for bipolarons

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.

4 page, 1 figure

Cited by in corpus (10)

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• Breakdown of the Wiedemann-Franz law in strongly-coupled electron-phonon system, application to the cuprates
• Diamagnetism of real-space pairs above Tc in hole doped cuprates
• High temperature superconductivity due to the long-range electron-phonon interaction, application to isotope effects, thermomagnetic transport and nanoscale heterogeneity in cuprates
• Hall-Lorenz number paradox in cuprate superconductors
• Bipolaronic proximity and other unconventional effects in cuprate superconductors