2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/209665The mechanism of field-effect doping in the "123" high critical temperature superconductors (HTS) has been investigated by x-ray absorption spectroscopy in the presence of an electric field. We demonstrate that holes are created at the CuO chains of the charge reservoir and that field-effect doping of the CuO2 planes occurs by charge transfer, from the chains to the planes, of a fraction of the overall induced holes. The electronic properties of the charge reservoir and of the dielectric/HTS interface determine the electric field doping of the CuO2 planes4 pages, 4 figures, Phys. Rev. Lett. accepted January (2008)Strongly Correlated ElectronsSuperconductivitytext