Effect of magnetic-field-induced frustration on the superconducting transition of proximity-coupled arrays

The magnetic field dependence of the superconducting transition has been studied in triangular arrays of Pb-Sn proximity-coupled junctions. The transition temperature T/sub c/ and the array resistance R(T) are found to vary periodically in a perpendicular magnetic field with a period corresponding to one flux quantum per unit cell of the array. In addition, both quantities show substructure at rational fractions of a flux quantum f = Phi/Phi0 = (1/4),(1/3),1 /2,(2/3),(3/4). The current-voltage characteristics of the arrays are nonlinear at temperatures near the transition temperature T/sub c/, with voltage increasing as a power of the current Vapprox.I/sup a/(T,f). As a function of reduced temperature t = [T/sub c/(f)-T]/T/sub c/(f), the power-law exponent a(t,f) is insensitive to f