Currents in metallic rings with quantum dot

TL;DR

This paper investigates how quantum dots influence magnetic currents in metallic rings, comparing classical and quantum thermal fluctuation models, and identifying conditions for paramagnetic to diamagnetic transitions.

Contribution

It introduces a framework combining classical and quantum fluctuation models to analyze current behavior in metallic rings with quantum dots, revealing flux response transitions.

Findings

Quantum and classical fluctuation models can both produce paramagnetic to diamagnetic transitions.

Transmission properties of the quantum dot significantly affect current characteristics.

Parameter regimes exist where the ring's magnetic response switches based on flux and quantum dot properties.

Abstract

Currents in a metallic ring with a quantum dot are studied in the framework of a Langevin equation for a magnetic flux passing through the ring. Two scenarios are considered: one in which thermal fluctuations of the dissipative part of the current are modelled by classical Johnson-Nyquist noise and one in which quantum character of thermal fluctuations is taken into account in terms of a quantum Smoluchowski equation. The impact of the amplitude and phase of the transmission coefficient of the electron through a quantum dot on current characteristics is analyzed. In tailored parameter regimes, both scenarios can exhibit the transition from para-- to diamagnetic response of the ring current versus external magnetic flux.