Universal Quantum Fluctuation-Dissipation Relation for Systems Far From Equilibrium

TL;DR

This paper introduces a universal nonequilibrium fluctuation-dissipation theorem for quantum systems far from equilibrium, revealing additional correlations governed by quantum curl flux, with applications to molecular junctions and quantum thermodynamics.

Contribution

It presents a general nonequilibrium FDT for quantum Markovian processes where detailed balance is broken, extending the scope beyond near-equilibrium conditions.

Findings

Derived a quantum nonequilibrium FDT applicable to far-from-equilibrium systems.

Identified quantum curl flux as a key factor in relaxation and fluctuations.

Applied the theory to molecular junctions, showing effects on optical spectra.

Abstract

Fluctuations associated with relaxations in far-from-equilibrium regime is of fundamental interest for a large variety of systems within broad scales. Recent advances in techniques such as spectroscopy have generated the possibility for measuring the fluctuations of the mesoscopic systems in connection to the relaxation processes when driving the underlying quantum systems far from equilibrium. We present a general nonequilibrium Fluctuation-Dissipation Theorem (FDT) for quantum Markovian processes where the detailed-balance condition is violated. Apart from the fluctuations, the relaxation involves extra correlation that is governed by the quantum curl flux emerged in the far-from-equilibrium regime. Such a contribution vanishes for the thermal equilibrium, so that the conventional FDT is recovered. We finally apply the nonequilibrium FDT to the molecular junctions, elaborating the detailed-balance-breaking effects on the optical transmission spectrum. Our results have the advantage of and exceed the scope of the fluctuation-dissipation relation in the perturbative and near equilibrium regimes, and is of broad interest for the study of quantum thermodynamics.ation in the perturbative and near equilibrium regimes, and is of broad interest for the study of quantum thermodynamics.