Availing non-Markovian dynamics in effective negative temperature-based transient quantum Otto engines

TL;DR

This paper explores how non-Markovian dynamics can enhance the efficiency of negative temperature quantum Otto engines during finite-time processes, revealing that partial thermalization can outperform traditional full thermalization.

Contribution

It introduces the concept of necessarily transient quantum Otto engines operating in extended temperature domains, demonstrating the impact of non-Markovianity on engine performance and operational range.

Findings

Maximum efficiency increases with non-Markovianity.

Overall performance decreases as non-Markovianity increases.

Extended operational temperature domain with non-Markovian effects.

Abstract

We demonstrate that the efficiency of effective negative temperature-based quantum Otto engines, already known to outperform their traditional counterparts operating with positive-temperature thermal reservoirs, can be further improved by terminating the isochoric strokes before the working substance reaches perfect equilibrium with its environment. Our investigation encompasses both Markovian and non-Markovian dynamics during these finite-time isochoric processes while considering a weak coupling between the working substance and the reservoirs. We assess the performance of these engines as they undergo a transition from the Markovian to the non-Markovian regime using two figures of merit: maximum achievable efficiency at a certain finite time during the isochoric heating stroke, and overall performance of the engine over an extended period during the transient phase of this stroke. We show that the maximum efficiency increases with the increase of non-Markovianity. However, the overall engine performance decreases as non-Markovianity increases. Additionally, we discover the existence of effective negative temperature-based necessarily transient quantum Otto engines. These engines operate within an extended operational domain, reaching into temperature ranges where conventional effective negative temperature-based quantum Otto engines, which rely on perfect thermalization during the isochoric strokes, are unable to function. Furthermore, this extended operational domain of an effective negative temperature-based necessarily transient quantum Otto engine increases as non-Markovianity becomes more pronounced.