Tailoring the intrinsic doping at YBa₂Cu₃O ₇-metal-contacts

Charge redistribution at interfaces between high-T_c superconductors and metals is problematic for technological applications due to local variations in the electronic structure. In particular, the interface affects the charge density in the superconducting CuO₂-planes. For obtaining quantitative insight into effects of interface doping, we address YBCO-metal-contacts by means of first principle supercell calculations within density functional theory. On the one hand, we find that the CuO ₂-planes are intrinsically electron-overdoped, i.e. hole-underdoped. On the other hand, very strong effects on the near-contact electronic states are also caused by electronegative impurities incorporated into the metal. Doping of such impurities consequently paves the way for a controlled re-extracting of charge from intrinsically doped interfaces and, therefore, for a tailoring of the interface properties.