Electric-field effect on transport and superconducting properties of YBa2Cu3O7-x

Charging effects on the transport properties of thin YBa2Cu3O7-x (YBCO) films are measured using FET-like junctions of YBCO in thickness ranging from 1 to 10 unit-cell thicknesses (UCT's). An electric (E) field experiment without magnetic field reveals that the conductance is divergent at finite temperatures and changes of the Kosterlitz-Thouless transition temperature are observed as a function of applied E field. Under magnetic fields, the temperature dependence of the resistance under E fields is of Arrhenius type, and E field effects on the pinning energy of vortex are evaluated. These changes of the superconducting properties are linearly correlated to those of the normal resistance, namely, the induced areal carrier densities.