Quasistates in a ring coupled to a reservoir and their relation to the Dicke effect

TL;DR

This paper investigates how a mesoscopic ring coupled to a reservoir exhibits quasistates and long-living states, drawing an analogy to the Dicke effect, and provides a new stable energy spectrum at strong coupling.

Contribution

It introduces a model linking quasistates in a ring to the Dicke effect, revealing a new stable energy spectrum under strong coupling conditions.

Findings

Development of quasistates with sharp eigenenergies at strong coupling.

Identification of long-living states analogous to the Dicke effect.

Reproduction of previous scattering matrix results and discovery of a new stable spectrum.

Abstract

We study the energy spectrum and the persistent current in an ideal one-dimensional mesoscopic ring coupled to an external fermionic reservoir. The contact between ring and reservoir is described by a tunneling operator, which causes an indirect coupling between different ring states via states in the reservoir. For strong coupling to the reservoir new quasistates with sharp eigenenergies develop inside the ring. The formation of long-living states at strong tunnel coupling to the reservoir is analogous to the Dicke effect in optics, that was recently investigated in context of resonant scattering and resonant tunneling in solid state systems. Our model reproduces the results obtained in previous work based on the scattering matrix approach and furthermore it describes a new stable energy spectrum in the limit of strong coupling.