Persistent currents in nanorings and quantum decoherence by Coulomb interaction

TL;DR

This paper analyzes how Coulomb interactions cause quantum decoherence in persistent currents of electrons in nanorings, showing exponential suppression at low temperatures and large ring sizes, highlighting interaction-driven decoherence.

Contribution

It provides a non-perturbative analysis of persistent currents considering electron-electron interactions using instanton techniques, revealing a temperature-independent dephasing length.

Findings

Persistent current is exponentially suppressed at large ring perimeters.

Dephasing length is set by interactions and independent of temperature.

Demonstrates quantum decoherence driven by electron-electron interactions at zero temperature.

Abstract

Employing instanton technique we evaluate equilibrium persistent current (PC) produced by a quantum particle moving in a periodic potential on a ring and interacting with a dissipative environment formed by diffusive electron gas. The model allows for detailed non-perturbative analysis of interaction effects and -- depending on the system parameters -- yields a rich structure of different regimes. We demonstrate that at low temperatures PC is exponentially suppressed at sufficiently large ring perimeters $2\pi R> L_{\varphi}$ where the dephasing length $L_{\varphi}$ is set by interactions and does not depend on temperature. This behavior represents a clear example of quantum decoherence by electron-electron interactions at $T\to 0$.