Finite-time quantum Otto engine: Surpassing the quasi-static efficiency due to friction

TL;DR

This paper investigates finite-time quantum Otto engines with different baths, revealing that friction can enhance performance beyond quasi-static limits and that nonequilibrium working fluids can outperform equilibrium ones.

Contribution

It provides exact solutions for two types of finite-time quantum Otto cycles and compares their performance, highlighting counterintuitive effects of friction and nonequilibrium conditions.

Findings

Agarwal engine's performance exceeds quasi-static Otto efficiency due to friction.

Lindbladian engine maintains nonzero power in short-time regimes.

Nonequilibrium working fluids can outperform equilibrium ones in quantum heat engines.

Abstract

In finite-time quantum heat engines, some work is consumed to drive a working fluid accompanying coherence, which is called `friction'. To understand the role of friction in quantum thermodynamics, we present a couple of finite-time quantum Otto cycles with two different baths: Agarwal versus Lindbladian. We solve them exactly and compare the performance of the Agarwal engine with that of the Lindbladian engine. In particular, we find remarkable and counterintuitive results that the performance of the Agarwal engine due to friction can be much higher than that in the quasistatic limit with the Otto efficiency, and the power of the Lindbladian engine can be nonzero in the short-time limit. Based on additional numerical calculations of these outcomes, we discuss possible origins of such differences between two engines and reveal them. Our results imply that even with an equilibrium bath, a nonequilibrium working fluid brings on the higher performance than what an equilibrium working fluid does.