Equilibrium currents in quantum double ring system: A non-trivial role of system-reservoir coupling

TL;DR

This paper investigates how the coupling strength between a quantum double ring system and a reservoir affects equilibrium currents and magnetic moments, revealing significant deviations from classical expectations at strong coupling.

Contribution

It introduces a simple S-Matrix model to analyze the impact of system-reservoir coupling on equilibrium currents in mesoscopic quantum rings.

Findings

Agreement between current definitions at weak coupling

Disagreement emerges at strong coupling

Coupling strength critically influences mesoscopic magnetic properties

Abstract

Amperes law states that the magnetic moment of a ring is given by current times the area enclosed. Also from equilibrium statistical mechanics it is known that magnetic moment is the derivative of free energy with respect to magnetic field. In this work we analyze a quantum double ring system interacting with a reservoir. A simple S-Matrix model is used for system-reservoir coupling. We see complete agreement between the aforesaid two definitions when coupling between system and reservoir is weak, increasing the strength of coupling parameter however leads to disagreement between the two. Thereby signifying the important role played by the coupling parameter in mesoscopic systems.