Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling

TL;DR

This paper develops a unified theoretical framework for quantum energy transfer in the nonequilibrium spin-boson model, covering weak to strong coupling regimes and explaining various observed phenomena.

Contribution

It introduces a nonequilibrium polaron-transformed Redfield equation that analytically evaluates energy flux across different coupling strengths.

Findings

Bridges transfer dynamics from weak to strong coupling smoothly.

Explains coherence-enhanced heat flux phenomena.

Shows absence of negative differential thermal conductance.

Abstract

We investigate the microscopic mechanism of quantum energy transfer in the nonequilibrium spin-boson model. By developing a nonequilibrium polaron-transformed Redfield equation based on fluctuation decoupling, we dissect the energy transfer into multi-boson associated processes with even or odd parity. Based on this, we analytically evaluate the energy flux, which smoothly bridges the transfer dynamics from the weak spin-boson coupling regime to the strong-coupling one. Our analysis explains previous limiting predictions and provides a unified interpretation of several observations, including coherence-enhanced heat flux and absence of negative differential thermal conductance in the nonequilibrium spin-boson model. The results may find wide applications for the energy and information control in nanodevices.