Effect of Disorder on the Quantum Coherence in Mesoscopic Wires

TL;DR

This study investigates how disorder affects quantum coherence in mesoscopic wires, revealing a new regime where coherence time is disorder-independent and challenging previous saturation assumptions.

Contribution

It demonstrates a transition from diffusive to semi-ballistic regimes and uncovers a disorder-independent coherence time in the latter, with implications for understanding decoherence.

Findings

Coherence time follows a power law with diffusion coefficient in diffusive limit.

In semi-ballistic regime, coherence time becomes independent of disorder.

No saturation observed in temperature dependence down to lowest temperatures.

Abstract

We present phase coherence time measurements in quasi-one-dimensional mesoscopic wires made from high mobility two-dimensional electron gas. By implanting gallium ions into a GaAs/AlGaAs heterojunction we are able to vary the diffusion coefficient over 2 orders of magnitude. We show that in the diffusive limit, the decoherence time follows a power law as a function of diffusion coefficient as expected by theory. When the disorder is low enough so that the samples are semi-ballistic, we observe a new and unexpected regime in which the phase coherence time is independent of disorder. In addition, for all samples the temperature dependence of the phase coherence time follows a power law down to the lowest temperatures without any sign of saturation and strongly suggests that the frequently observed low temperature saturation is not intrinsic.