Breakdown of correlated diffusion in quasiballistic quantum wires at high magnetic fields.

Abstract

We study the universal conductance fluctuations (UCF) observed in the low-temperature magnetoconductance of high-mobility GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As quantum wires. As the magnetic field is increased, such that the cyclotron orbit becomes smaller than the wire width, both the amplitude \ensuremath{\delta}g and correlation field ${\mathit{B}}_{\mathit{c}}$ of the fluctuations are found to increase linearly with magnetic field. The linear increase in ${\mathit{B}}_{\mathit{c}}$ is in agreement with the results of recent nonlocal studies of the UCF, and is thought to demonstrate a transition to edge-related transport. Similarly, the increase in \ensuremath{\delta}g is argued to result from a magnetically induced breakdown of correlated diffusion, which occurs as the edge states begin to be resolved. Such a breakdown was not observed in previous studies of dirty wires, in which the electron motion remains diffusive up to very high fields, but is instead thought to result from the quasiballistic nature of the wires we study.