Quantum fluctuations in n⁺ GaAs wires with invasive probes

Conductance fluctuations in mesoscopic electronic systems depend strongly on the configuration of the measurement probes. We have found striking differences in the magnetoconductance fluctuations of n+ GaAs wires when measured in the longitudinal and Hall geometries. In our experiments, the elastic scattering length is smaller than the channel width, which is smaller than the phase coherence length which is comparable to the probe width. The voltage fluctuations and correlation fields of the conductance fluctuations are more than an order of magnitude larger in the longitudinal probe geometry than in the Hall geometry. These differences shed new light on mesoscopic transport phenomena and can be explained by extension of a recently developed multi-lead formalism. © 1990.