Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 10: Superconductivity - Properties, Electronic Structure, Order Parameter

TT 10.5: Talk

Tuesday, March 27, 2007, 10:30–10:45, H18

Charge(re)distribution at YBCO/metal interfaces: screened band bending — •Cosima Schuster and Udo Schwingenschlögl — Institut für Physik, Universität Augsburg, 86135 Augsburg

The functionality of nanoscale devices depends crucially on the transport properties across the interfaces. Especially, the transport mechanism in electronic devices based on high-T_c-superconductors is of special interest, in particular the charge density within the superconducting CuO₂ planes in the vicinity of an interface or grain boundary. Main questions in this context are interface charging, band bending, or contact resistivity. We calculate the local electronic structure of an YBCO/metal interface using density functional theory (using the Wien2k code) in two different geometries (where the interface is either parallel or perpendicular to the CuO₂ planes), including an optimization of the atomic positions near the interface. We consider supercells with 4 metal and 2 YBCO or 6 metal and 3 YBCO units, respectively. For the parallel contact we find a transfer of holes out of the CuO₂ planes resulting in shift to the underdoped regime of the high-T_c phase diagram. Thus, this geometry reflects the properties of a grain boundary. The results are neither dependent on contact geometry, nor the contact metal, or interface plane.