Influences of homogeneous and inhomogeneous magnetic fields on the performance of a quantum Stirling heat engine

Abstract

In this paper, a quantum heat engine (QHE) and a quantum refrigerator (QR) are theoretically studied using a quantum Stirling cycle (SC). The machine works with a working substance consisting of a two-qubit Heisenberg XYZ model under both homogeneous and inhomogeneous magnetic fields, and the Dzyaloshinskii-Moriya interaction (DMI). The influences of both magnetic fields are studied on the absorbed, and released heat, work done, efficiency, and performance coefficient (PC) of the Stirling engine and refrigerator. The findings show that the SC can operate as a QHE or QR. It depends on the proper selection of the system parameters. We can obtain a QHE or a QR with acceptable efficiency or performance coefficient. To this end, we increase both magnetic fields and choose suitable values for other system parameters thereby obtaining higher values for the PC. Also, we reduce both magnetic fields and obtain higher values for the efficiency of QHE. Considering homogeneous and inhomogeneous magnetic fields have different effects on machine efficiency, and refrigerator performance.