NONLOCAL PARACONDUCTANCE OF SMALL SUPERCONDUCTING LOOPS

The nonlocal current response to an electric field characteristic of the superconducting state has been predicted to be observable above the transition temperature T(c) over a length scale set by the correlation length for superconducting fluctuations, xi(T). A manifestation of this effect has been found in a multiterminal measurement of a square superconducting loop of characteristic size, L is similar to xi(T). The ratio of the voltages measured by two different sets of probes attached at different positions is observed to oscillate as a function of the flux threading the loop. This nonlocal effect is distinct from analogous phenomena associated with the coherent transport of electrons in mesoscopic structures.