Anomalous Heat Transfer in Nonequilibrium Quantum Systems

TL;DR

This paper classifies mechanisms behind anomalous heat transfer in nonequilibrium quantum systems, revealing the roles of initial correlations, interactions, and temperature inhomogeneity, with implications for quantum thermal machine design.

Contribution

It provides a comprehensive classification of AHT mechanisms in quantum systems from a quantum-information perspective, highlighting the necessity of quantum coherence in certain cases.

Findings

AHT can originate from initial correlation, intrasystem interaction, and temperature inhomogeneity.

Quantum coherence is necessary for AHT in two-body interaction systems.

Explicit examples of AHT mechanisms in three-qubit systems.

Abstract

Anomalous heat transfer (AHT), a process by which heat spontaneously flows from a cold system into a hot one, superficially contradicts the Clausius statement of the second law of thermodynamics. Here we provide a full classification of mechanisms of the AHT in nonequilibrium quantum systems from a quantum-information perspective. For initial states in local equilibrium, we find that the AHT can arise from three resources: initial correlation, intrasystem interaction, and intrasystem temperature inhomogeneity. In particular, for qubit systems, we prove that initial quantum coherence is necessary for AHT if the intersystem interactions are limited to the two-body type. We explicitly show the AHT dominated by each of the mechanisms in a three-qubit system. Our classification scheme may offer a guideline for developing high-efficiency quantum autonomous thermal machines.