Dimensional Crossover of the Dephasing Time in Disordered Mesoscopic Rings

TL;DR

This paper investigates how dephasing time in disordered mesoscopic rings transitions from diffusive to zero-dimensional behavior as temperature decreases, using quantum noise models and analyzing magnetoconductivity and oscillations.

Contribution

It provides a theoretical analysis of the crossover in dephasing time in mesoscopic rings, linking it to observable oscillation signatures and extending understanding of dephasing in low-dimensional systems.

Findings

Dephasing time exhibits a crossover from diffusive/ergodic to 0D behavior.

The crossover can be observed in magnetoconductivity and AAS oscillation amplitudes.

The study predicts the temperature dependence of dephasing in ring geometries.

Abstract

We study dephasing by electron interactions in a small disordered quasi-one dimensional (1D) ring weakly coupled to leads. We use an influence functional for quantum Nyquist noise to describe the crossover for the dephasing time $\Tph (T)$ from diffusive or ergodic 1D ($ \Tph^{-1} \propto T^{2/3}, T^{1}$) to 0D behavior ($\Tph^{-1} \propto T^{2}$) as $T$ drops below the Thouless energy. The crossover to 0D, predicted earlier for 2D and 3D systems, has so far eluded experimental observation. The ring geometry holds promise of meeting this longstanding challenge, since the crossover manifests itself not only in the smooth part of the magnetoconductivity but also in the amplitude of Altshuler-Aronov-Spivak oscillations. This allows signatures of dephasing in the ring to be cleanly extracted by filtering out those of the leads.