We discuss the voltage dependence of the differential conductance fluctuations in metal samples containing a disordered region much smaller than the inelastic diffusion length at low voltage. Measurements are made for an ensemble of different defect configurations within the same sample. We find that the root mean square amplitude of differential conductance fluctuations within a phase coherent sample is independent of voltage, in conflict with existing theory. The measured voltage correlation scale is at least an order of magnitude smaller than the Thouless energy divided by e.

• Received 5 October 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.986