Eur. Phys. J. D (2014) 68: 32
https://doi.org/10.1140/epjd/e2013-40536-0

Regular Article

Quantum Stirling heat engine and refrigerator with single and coupled spin systems

¹ School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, P.R. China
² School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, P.R. China
³ College of Mathematics and Physics, Bohai University, Jinzhou 121013, P.R. China

^a e-mail: ghost820521@163.com
^b e-mail: yixx@dlut.edu.cn

Received: 29 August 2013
Received in final form: 20 November 2013
Published online: 20 February 2014

Abstract

We study the reversible quantum Stirling cycle with a single spin or two coupled spins as the working substance. With the single spin as the working substance, we find that under certain conditions the reversed cycle of a heat engine is NOT a refrigerator, this feature holds true for a Stirling heat engine with an ion trapped in a shallow potential as its working substance. The efficiency of quantum Stirling heat engine can be higher than the efficiency of the Carnot engine, but the performance coefficient of the quantum Stirling refrigerator is always lower than its classical counterpart. With two coupled spins as the working substance, we find that a heat engine can turn to a refrigerator due to the increasing of the coupling constant, this can be explained by the properties of the isothermal line in the magnetic field-entropy plane.