Non-equilibrium quantum heat machines

TL;DR

This paper extends the concept of quantum heat machines to non-equilibrium environments, classifying their thermodynamic behavior and establishing a generalized Carnot efficiency limit for such systems.

Contribution

It introduces a classification of non-equilibrium baths and demonstrates that heat machines operating with these baths are still bounded by a generalized Carnot efficiency.

Findings

Non-equilibrium baths can be classified based on thermodynamic behavior.

Efficiency of machines with non-equilibrium baths is limited by a generalized Carnot bound.

The framework applies to systems like solar cells, biological machines, and laser-driven nanodevices.

Abstract

Standard heat machines (engine, heat pump, refrigerator) are composed of a system ("working fluid") coupled to at least two equilibrium baths at different temperatures and periodically driven by an external device (piston or rotor) called sometimes work reservoir. The aim of this paper is to go beyond this scheme by considering environments which are stationary but cannot be decomposed into few baths at thermal equilibrium. Such situations are important, for example in solar cells, chemical machines in biology, various realizations of laser cooling or nanoscopic machines driven by laser radiation. We classify non-equilibrium baths depending on their thermodynamic behavior and show that the efficiency of heat machines operating under their influences is limited by a generalized Carnot bound.