Intrinsic doping at YBCO-metal interfaces: Quantitative results

Charge redistribution in high-T_c superconductors due to structural defects or interfaces is known to be crucial for electronic applications as the band structure is modified on a local scale. In order to investigate these effects in more detail, we address the normal-state properties of YBa₂Cu₃O₇ (YBCO) in the vicinity of YBCO-metal interfaces by electronic structure calculations for well relaxed interface configurations. Our findings can be interpreted in terms of a band-bending mechanism complemented by local screening effects. We derive quantitative results for the intrinsic doping of the superconducting CuO ₂ planes due to the metal interface. In particular, the net charge transfer amounts to 0.13 electrons in favour of each intraplane copper site, which appears to be a typical value for interfaces of high-T_c superconductors, thus opening great possibilities for a systematic optimization of wires and tapes from high-T_c materials.