Thermodynamic Bounds on Efficiency for Systems with Broken Time-reversal Symmetry

TL;DR

This paper derives bounds on efficiency for systems with broken time-reversal symmetry, showing that maximum efficiency and efficiency at maximum power depend on two parameters, and that Carnot efficiency can be approached under different conditions.

Contribution

It introduces a framework to determine efficiency bounds in systems with broken time-reversal symmetry, highlighting the roles of a figure of merit and an asymmetry parameter.

Findings

Maximum efficiency depends on a figure of merit and an asymmetry parameter.

Carnot efficiency can be approached at lower figure of merit values.

Efficiency at maximum power can surpass the Curzon-Ahlborn limit within linear response.

Abstract

We show that for systems with broken time-reversal symmetry the maximum efficiency and the efficiency at maximum power are both determined by two parameters: a "figure of merit" and an asymmetry parameter. In contrast to the time-symmetric case, the figure of merit is bounded from above; nevertheless the Carnot efficiency can be reached at lower and lower values of the figure of merit and far from the so-called strong coupling condition as the asymmetry parameter increases. Moreover, the Curzon-Ahlborn limit for efficiency at maximum power can be overcome within linear response. Finally, always within linear response, it is allowed to have simultaneously Carnot efficiency and non-zero power.