Persistent current noise in normal and superconducting nanorings

TL;DR

This paper studies fluctuations of persistent current in nanorings, showing they can persist at zero temperature due to environmental interactions or quantum phase slips, with coherence depending on dissipation and external flux.

Contribution

It reveals conditions under which persistent current noise remains coherent or becomes incoherent, highlighting the role of dissipation and external potentials in nanoring systems.

Findings

Persistent current noise can persist at zero temperature.

Quantum coherence in PC noise can be tuned by magnetic flux.

Dissipation suppresses coherence, making PC noise flux-independent.

Abstract

We investigate fluctuations of persistent current (PC) in nanorings both with and without dissipation and decoherence. We demonstrate that such PC fluctuations may persist down to zero temperature provided there exists either interaction with an external environment or an external (periodic) potential produced, e.g., by quantum phase slips in superconducting nanorings. Provided quantum coherence is maintained in the system PC noise remains coherent and can be tuned by an external magnetic flux $\Phi_x$ piercing the ring. If quantum coherence gets suppressed by interactions with a dissipative bath PC noise becomes incoherent and $\Phi_x$-independent.