Resistance fluctuations in multiprobe microstructures: Length dependence and nonlocality

We study numerically the resistance fluctuations, R, in a disordered metallic microstructure with several probes within a single quantum coherent region. The strong influence of the probes causes R to depend on the geometry of the coherent region. In a particular four-probe structure, R is only weakly dependent on the voltage probe separation, in agreement with experiment, while the strong dependence of R on separation in other structures should be experimentally observable. Nonlocal fluctuations decay slowly as the distance between the current path and voltage probes increases. © 1988 The American Physical Society.