Electric field effect in high <i>T</i> <i>c</i> superconducting ultrathin YBa2Cu3O7−<i>x</i> films

Abstract

A multilayer high Tc superconducting field-effect transistor-like structure was made from ultrathin YBa2Cu3O7−x films. An epitaxially grown dielectric SrTiO3 insulation layer, which had a forward bias breakdown voltage of about 20 V, allowed an electric field induced change in the channel layer of 1.25×1013 carrier/cm2 per volt of the gate voltage. A significant modulation of the normal state and superconducting properties was observed in samples with YBa2Cu3O7−x channel layers of a few unit cells thick. By applying gate voltage of different polarities, Tc was both suppressed and enhanced by ∼1 K. The resistance was modulated by as much as 20% in the normal state and by over 1500% near the zero resistance temperature.