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DF: Dielektrische Festkörper

DF 8: Dielektrische und ferroelektrische Schichten, Nanostrukturen und Rastermethoden

DF 8.9: Vortrag

Donnerstag, 27. März 2003, 12:30–12:50, HSZ/403

Electronic Charge-Polarization Coupling in Superconductor-Ferroelectric Superlattices — •Natalie Pavlenko and Franz Schwabl — Institut für Theoretische Physik T34, Physik-Department der TU München, James-Franck-Strasse, D-85747 Garching b. München, Germany

We present a theory of periodic ferroelectric-superconductor (FE-S) heterostructures containing ferroelectric (FE) layers sandwiched between superconducting films. We analyze the redistribution of the local electronic charge carrier density at the FE-S in terface in the presence of the spontaneous polarization in the ferroelectric layer. The effect of FE-S contacts on the ferroelectrics is found to be crucial leading to a structural transformation from the state with the homogeneous-type polarization to th e phase with a set of stable polarization domains. Even above the bulk ferroelectric critical temperature we find in the ferroelectric layer a stable contact-induced enhanced spontaneous polarization. An increase of the FE-S interface coupling results in a complex nonmonotonic behavior of the superconducting transition temperature and finally, for the strong-coupling regime, in a complete suppression of the superconductivity.

The behavior of the compounds is analyzed for different thicknesses of the FE- and S-films demonstrating the strong change of the topology of the theoretical phase diagrams with a variation of the films’ thickness. The results are hoped to be especially important for the analysis of high-temperature cuprate superconductor films grown on perovskite-type ferroelectrics.