Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 7: Superconductivity & Solids At Low Temperature - Poster Session

TT 7.16: Poster

Montag, 27. März 2006, 14:00–17:45, P1

Electronic structure calculations for YBCO/metal interfaces — •Udo Schwingenschlögl and Cosima Schuster — Institut für Physik, Universität Augsburg, 86135 Augsburg

Transport properties of heterostructures consisting of a metal and a correlated superconductor are of great importance for electronic devices based on HTSC. Using electronic structure calulations within density functional theory and the local density approximation, we investigate YBCO/metal interfaces. As the lattice mismatch between YBCO and Pd is rather small (0.7%), we choose Pd as the metallic constituent. It is generally accepted that the carrier density is modified at grain boundaries. Since this band bending should take place on the length scale of the lattice constant it can be reproduced by LDA supercell calculations. In particular, we use a supercell consisting of two YBCO unit cells alternating with five Pd layers along the orthorhombic c-axis. Following experimental results, the YBCO layers entering our calculations terminate by CuO chains.

Our results show that the electronic density of states at the interface depends crucially on the details of the local atomic structure. Therefore we have relaxed the atomic positions to minimize the forces on the ions. We compare two possible interface geometries, where the Pd atoms are placed on the Cu or O atoms of the CuO chains, respectively. For these configurations we determine the charge distribution across the interface.