K. Nakajima et al., FIELD EFFECTS ON THE DIELECTRIC PROPERTY OF YBCO BICRYSTAL GRAIN-BOUNDARY JUNCTIONS, IEEE transactions on applied superconductivity, 5(2), 1995, pp. 2861-2864
Electric field effects on YBCO boundary Josephson junctions combined w
ith MIS (Metal, Insulator, Superconductor) structures were studied. Cu
rrent steps and hysteresis recognized in current-voltage curves were s
trongly affected by the field. The current steps were attributed to th
e self-excited resonances, i.e., Fiske steps. Both the effects were in
terpreted by the field dependence of the effective dielectric constant
of the grain boundary which has a certain contribution from the large
dielectric constant of SrTiO3 substrates. The effective dielectric co
nstant normalized with barrier thickness of the junction was estimated
to be about 40 nm(-1) for the zero gate voltage and was decreased by
a factor of 2 with the electric field of +/-16kV/cm. This feature is a
ssumed adequate for tuning the phase velocity in the bicrystal grain b
oundaries.