Stroboscopic two-stroke quantum heat engines

TL;DR

This paper introduces a framework for stroboscopic, two-stroke quantum heat engines in chains, analyzing their dynamics, power optimization, and conditions for Otto efficiency, advancing quantum thermodynamics understanding.

Contribution

It generalizes the SWAP engine model using a collisional approach, fully characterizes transient dynamics, and identifies conditions for Otto efficiency regardless of reservoir settings.

Findings

Engine reaches a limit-cycle with energy localized at boundary sites.

Multiple power optimization strategies without efficiency loss.

Certain models operate at Otto efficiency under all conditions.

Abstract

The formulation of models describing quantum versions of heat engines plays an important role in the quest toward establishing the laws of thermodynamics in the quantum regime. Of particular importance is the description of stroke-based engines which can operate at finite-time. In this paper we put forth a framework for describing stroboscopic, two-stroke engines, in generic quantum chains. The framework is a generalization of the so-called SWAP engine and is based on a collisional model, which alternates between pure heat and pure work strokes. The transient evolution towards a limit-cycle is also fully accounted for. Moreover, we show that once the limit-cycle has been reached, the energy of the internal sites of the chain no longer changes, with the heat currents being associated exclusively to the boundary sites. Using a combination of analytical and numerical methods, we show that this type of engine offers multiple ways of optimizing the output power, without affecting the efficiency. Finally, we also show that there exists an entire class of models, characterized by a specific type of inter-chain interaction, which always operate at Otto efficiency, irrespective of the operating conditions of the reservoirs.