# Thermodynamic coupling rule for far-from-equilibrium systems

## TL;DR

This paper introduces a universal thermodynamic coupling rule that improves the performance of far-from-equilibrium systems, such as heat engines and refrigerators, by optimizing the interaction between energy and matter currents.

## Contribution

It proposes a new thermodynamic coupling rule applicable to diverse systems, enhancing efficiency and performance through proper flux interactions.

## Key findings

- Optimal coupling improves heat engine efficiency.
- Adjusting flux interactions enhances refrigerator performance.
- The rule applies universally across different system types.

## Abstract

The energy conversion efficiency of far-from-equilibrium systems is generally limited by irreversible thermodynamic fluxes that make contact with different heat baths. For complex systems, the states of the maximum efficiency and the minimum entropy production are usually not equivalent. Here we show that the proper adjustments of the interaction between the energy and matter currents offer some important criteria for the performance characterizations of thermal agents, regardless of the system types and transition protocols. The universal thermodynamic coupling rule plays a critical role in irreversible processes. A double quantum dot system is applied to demonstrate that the performances of heat engines or refrigrators can be enhanced by suitably adjusting the coupling strength between thermodynamic fluxes.