Low-temperature electron dephasing time in AuPd revisited

TL;DR

This paper revisits low-temperature electron dephasing times in AuPd alloys, revealing a systematic correlation with disorder level and proposing dynamical defects as a key cause for observed dephasing behavior.

Contribution

It identifies a universal scaling law for dephasing times in AuPd alloys and suggests dynamical structural defects as the primary dephasing mechanism at low temperatures.

Findings

Dephasing time scales inversely with diffusion constant, approximately as D^{-1}.

Low-temperature dephasing times are nearly temperature-independent.

Dynamical structural defects likely cause the observed dephasing behavior.

Abstract

Ever since the first discoveries of the quantum-interference transport in mesoscopic systems, the electron dephasing times, $\tau_\phi$, in the concentrated AuPd alloys have been extensively measured. The samples were made from different sources with different compositions, prepared by different deposition methods, and various geometries (1D narrow wires, 2D thin films, and 3D thickfilms) were studied. Surprisingly, the low-temperature behavior of $\tau_\phi$ inferred by different groups over two decades reveals a systematic correlation with the level of disorder of the sample. At low temperatures, where $\tau_\phi$ is (nearly) independent of temperature, a scaling $\tau_\phi^{\rm max} \propto D^{-\alpha}$ is found, where $tau_\phi^{\rm max}$ is the maximum value of $\tau_\phi$ measured in the experiment, $D$ is the electron diffusion constant, and the exponent $\alpha$ is close to or slightly larger than 1. We address this nontrivial scaling behavior and suggest that the most possible origin for this unusual dephasing is due to dynamical structure defects, while other theoretical explanations may not be totally ruled out.