Lorenz number in high Tc superconductors: evidence for bipolarons
preprintposted on 2006-03-31, 15:28 authored by K.K. Lee, A.S. Alexandrov, W.Y. Liang
Strong electron-phonon interaction in the 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.
NotesThis is a pre-print. The definitive version: LEE, ALEXANDROV and LIANG, 2003. Lorenz number in high Tc superconductors: evidence for bipolarons. Physical Review Letters, 90(21), is available at: http://prl.aps.org/.