Metallic and superconducting surfaces of YBa2Cu3O7 probed by electrostatic charge modulation of epitaxial films

Transport in YBa2Cu3O7 was studied by modulating the resistance and superconductive kinetic inductance via capacitively charging (001) surfaces. The mobility varies inversely with temperature, the effective mass is 5(+ or - 1) me at low temperature, and hole carrier densities are temperature independent and nearly the same in normal and superconducting states. Transition temperatures at ideal surfaces are equal to the bulk and show notably weak modulation with carrier density. (Author)