Large modulation of critical currents in high T/sub c/ superconducting field-effect (SUFET) devices

Various properties of ultrathin YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) films used in superconducting field effect 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 the present work, the authors have investigated the behavior of the critical current density, J/sub c/, in these devices. In 5-8-nm-thick YBCO films in such devices, J/sub c/ (T=4 K, B=0 T, 1 mu V/mm criterion) of up to 4*10/sup 5/ A/cm/sup 2/ has been observed. By applying moderate gate voltages(<30 V), J/sub c/ can be suppressed by up to 90%. An empirical description of the functional dependence J/sub c/(T,B,N) is given. Examination of the I-V characteristics yields V=a*I/sup alpha /, with alpha dependent on the gate voltage. The data are discussed in terms of the relative importance of field-induced depinning, thermal fluctuations, and pure geometrical effects.<>