NONLOCAL CONDUCTANCE OF SMALL SUPERCONDUCTING LOOPS IN THE PARACONDUCTIVE REGIME

Both quasiparticles and superconducting fluctuations contribute to the conductance of superconductors in the paraconductive regime slightly above the transition temperature. The fluctuation contribution consist s of the Maki-Thompson correction, which results from the scattering o f electrons by a superconducting fluctuation, and the Aslamazov-Larkin contribution which describes the conductivity of a fluctuating electr on pair. The latter is nonlocal over a length scale set by the fluctua tion correlation length, xi(T). The observation of this nonlocality in volves a multiterminal measurement of voltages in the paraconductive r egime of a square superconducting loop of characteristic size, L simil ar to xi(T). The ratio of the voltages measured by two different sets of probes attached to the loop at different positions is found to osci llate as a function of the flux threading the loop. This effect is dis tinct from phenomena associated with the coherent transport of electro ns in mesoscopic structures of a size smaller than the dephasing lengt h, L(phi).