Both quasiparticles and superconducting fluctuations contribute to the conductance of superconductors in the paraconductive regime slightly above the transition temperature. The fluctuation contribution consists of the Maki-Thompson correction, which results from the scattering of electrons by a superconducting fluctuation, and the Aslamazov-Larkin contribution which describes the conductivity of a fluctuating electron pair. The latter is nonlocal over a length scale set by the fluctuation correlation length, ξ(T). The observation of this nonlocality involves a multi-terminal measurement of voltages in the paraconductive regime of a square superconducting loop of characteristic size, L ∼ ξ(T). The ratio of the voltages measured by two different sets of probes attached to the loop at different positions is found to oscillate as a function of the flux threading the loop. This effect is distinct from phenomena associated with the coherent transport of electrons in mesoscopic structures of a size smaller than the dephasing length, Lφ.
Bibliographical noteFunding Information:
We thank L. I. Glazman for suggesting this problem, and for many helpful discussions. This work was supported by the National Science Foundation under Grant NSF/DMR-9303022.