Quantum heat engine efficiency of a small spin system with anisotropy
The rise of electronic devices lower than the nanoscale shifts the focus to quantum heat engines as they have improved features than their classical counterparts. In this work, the two-spin and three-spin systems using the Lipkin-Meshkov-Glick (LMG) model as the working substance of the heat engine are considered. The efficiency of the quantum heat engine comprised of two reversible isothermal processes and two isomagnetic processes with varying spin anisotropy is investigated. The configuration with the highest anisotropy was found to yield the highest efficiency for the two-spin system, and the most isotropic case was the most efficient for the three-spin system. This is attributed to the effect of anisotropy on the energy levels of the LMG spin system.