engleski

Bipolaron localization for increasing electron-phonon coupling in a small cluster

By exact diagonalization of a small cluster, we show that an interplay of electron-phonon and onsite electron-electron interactions results in ``intersite'' or ``onsite'' two-electron (bipolaronic) solutions of the Holstein-Hubbard model, depending on the strenghts of the interactions. On this basis, we argue that the decrease in the superconducting transition temperature of Bi-2212 compounds, following the enhancement of the electron-phonon interaction recently reported by Devereaux {\it et al.\/},\cite{Devereaux} might be a consequence of the above mechanism, which leads to a transition from itinerant (intersite) to bound immobile (onsite) bipolarons thus effectively reducing the number of superconducting carriers.

High-Tc superconductivity; cuprates; electron-electron interactions; electron-phonon interactions

nije evidentirano