Second-law-allowed temporal cooling of the coldest reservoir without external refrigeration

TL;DR

This paper demonstrates that in non-equilibrium quantum thermodynamics, it is possible to transiently cool the coldest reservoir without external refrigeration by exploiting heat transfer that complies with the Clausius inequality, with implications for quantum thermal machines.

Contribution

It reveals that transient cooling of the coldest reservoir is achievable through non-monotonic temperature and chemical potential evolution, expanding understanding of quantum thermodynamic processes.

Findings

Heat transfer from cold to hot reservoirs is allowed by Clausius inequality.

Transient cooling of the coldest reservoir without external refrigeration is possible.

Non-monotonic evolution of reservoirs' temperatures and chemical potentials can occur.

Abstract

Non-equilibrium quantum thermodynamics is an intensively developing field with many existing applications. We study the dynamics of temperatures and chemical potentials of fermionic reservoirs coupled to an open quantum system. We show that heat transfer from the coldest reservoir to the hottest one is allowed by the Clausius inequality and results in transient cooling of the coldest reservoir without additional external refrigeration. We show that during the establishment of thermal and chemical equilibrium, non-monotone evolution of reservoirs' temperatures and chemical potentials is possible, including changes in reservoirs' temperatures and chemical potentials orderliness. Achieved results can be used in the design of quantum thermal machines and nanoelectronic devices.