Low-temperature Dephasing and Renormalization in Model Systems

TL;DR

This paper explores low-temperature dephasing in various quantum systems, distinguishing it from renormalization effects, and examines its impact on coherence, correlation functions, and interference phenomena across different models.

Contribution

It provides a comparative analysis of dephasing mechanisms in spin-boson, Caldeira-Leggett, and particle-field interaction models, highlighting their differences and implications.

Findings

Dephasing affects both non-equilibrium and equilibrium quantum states.

Distinction between dephasing and renormalization effects is crucial.

Results applicable to quantum state engineering and mesoscopic systems.

Abstract

We investigate low-temperature dephasing in several model systems, where a quantum degree of freedom is coupled to a bath. Dephasing, defined as the decay of the coherence of inital non-equilibrium states, also influences the dynamics of equilibrium correlation and response functions, as well as static interference effects. In particular in the latter case dephasing should be distinguished from renormalization effects. For illustration, and because of its relevance for quantum state engineering in dissipative environments, we first reconsider dephasing in spin-boson models. Next we review Caldeira-Leggett models, with applications, e.g., to persistent currents in mesoscopic rings. Then, we analyze the more general problem of a particle which interacts with a quantum field V(t,r(t)), the fluctuations of which are characterized by a dielectric function epsilon(omega,k). Finally, we compare this model, both the formulation as well as the results, to the problem of interacting electrons in a diffusive conductor.