Nonlocal magnetoresistance of diffusive wires in high magnetic fields

Abstract

We have used a nonlocal configuration of measurement probes to study the magnetoresistance of diffusive n +-GaAs wires at high magnetic fields where ω cτ>1. At low temperatures we observe universal conductance fluctuations (UCF). For ω cτ>1 there is a large increase in the Lee-Stone correlation field but the amplitude is unchanged in strong disagreement with the theoretical prediction. We conclude that the UCF in this regime cannot be scaled in terms of a single parameter, the phase coherence length. At higher temperatures, where the UCF are quenched, we observe qualitatively new magnetoresistance oscillations which have the same periodicity as Shubnikov-de Haas oscillations but differ from them in many important respects. In particular, the new oscillations disappear at low temperatures. This indicates the importance of dissipation in the measurement of nonlocal resistance. There is excellent agreement between the temperature dependence of the new oscillations and a simple model.