Signatures of a Noise-Induced Quantum Phase Transition in a Mesoscopic Metal Ring

TL;DR

This paper investigates how electromagnetic noise with specific spectral properties can induce a quantum phase transition in a mesoscopic metal ring with a quantum dot, affecting persistent current responses.

Contribution

It demonstrates the signatures of noise-induced quantum phase transitions in mesoscopic rings, focusing on observable effects in persistent currents under different noise spectra.

Findings

Signatures of quantum phase transition observed in persistent current responses.

Robust effects identified for ohmic and subohmic noise spectra.

Environmental noise can control quantum states in mesoscopic systems.

Abstract

We study a mesoscopic ring with an in-line quantum dot threaded by an Aharonov-Bohm flux. Zero-point fluctuations of the electromagnetic environment capacitively coupled to the ring, with $\omega^s$ spectral density, can suppress tunneling through the dot, resulting in a quantum phase transition from an unpolarized to a polarized phase. We show that robust signatures of such a transition can be found in the response of the persistent current in the ring to the external flux as well as to the bias between the dot and the arm. Particular attention is paid to the experimentally relevant cases of ohmic ($s=1$) and subohmic ($s=1/2$) noise.