Large Modulation of Critical Currents in High TC Superconducting Field -Effect (Sufet) Devices

Various properties of ultrathin YBa2Cu3O7-δ (YBCO) films used in superconducting field effect (SuFET) devices have been shown to vary as a function of the applied gate voltage, i. e. by variation of the areal charge carrier density N. In this paper we investigate the behavior of the critical current density, Jc, in these devices. In 5 to 8 nm thick YBa2Cu3O7-δ films in such devices Jc (T = 4K, B = 0T, lμV/mm criterion) of up to 4x105 A/cm2 have been observed. By applying moderate gate voltages (< 30V) Jc can be suppressed by up to 90%. An empirical description of the functional dependence JC(T,B,N) is given. Examination of I-V characteristics yields V=a-Iα with a dependent on the gate voltage Vg. The data are discussed in terms of the relative importance of field induced depinning, thermal fluctuations, and pure geometrical effects.