Persistent current noise and electron-electron interactions

TL;DR

This paper studies how electron-electron interactions affect persistent current fluctuations in a quantum ring, showing that interactions can either preserve or suppress quantum coherence depending on their strength and the ring size.

Contribution

It provides a detailed analysis of persistent current noise in quantum rings considering electron-electron interactions, revealing conditions for coherence and incoherence at zero temperature.

Findings

Weak interactions and small ring radius preserve PC coherence.

Strong interactions or large rings suppress coherence and induce incoherent noise.

Persistent current noise persists at zero temperature regardless of interactions.

Abstract

We analyze fluctuations of persistent current (PC) produced by a charged quantum particle moving in a ring and interacting with a dissipative environment formed by diffusive electron gas. We demonstrate that in the presence of interactions such PC fluctuations persist down to zero temperature. In the case of weak interactions and/or sufficiently small values of the ring radius $R$ PC noise remains coherent and can be tuned by external magnetic flux $\Phi_x$ piercing the ring. In the opposite limit of strong interactions and/or large values of $R$ fluctuations in the electronic bath strongly suppress quantum coherence of the particle down to $T=0$ and induce incoherent $\Phi_x$-independent current noise in the ring which persists even at $\Phi_x=0$ when the average PC is absent.