Quantum Ising Heat Engines: A mean field study

TL;DR

This study investigates the efficiency of classical and quantum Ising heat engines using mean field dynamics, revealing that efficiencies are below Carnot limits but can be enhanced with specific field configurations.

Contribution

It provides a mean field framework for analyzing quantum and classical Ising heat engines and explores conditions for efficiency enhancement in mixed-field scenarios.

Findings

Efficiencies are below Carnot limits in both classical and quantum cases.

Analytical and numerical results agree well for efficiency estimates.

Efficiency can be increased in mixed-field Ising engines with specific field parameters.

Abstract

We have studied the efficiencies of both classical and quantum heat engines using an Ising model as working fluid and the mean field equation for its non-equilibrium dynamics, formulated earlier\cite{acs,ac} to study the dynamical hysteresis and the dynamical phase transitions in the quantum Ising ferromagnets. We studied numerically the Ising magnet's nonintegrable coupled nonlinear first order differential equations of motion for a four stroke heat engine and compared the efficiencies in both classical and quantum limits using the quasi-static approximation. In both the pure classical and pure quantum cases, the numerically calculated efficiencies are much less than the corresponding Carnot values. Our analytical formulations of the efficiencies (both in pure classical as well as in pure quantum Ising heat engines) are found to agree well with the numerical estimates. Such formulations also indicate increased efficiency for the mixed case of a transverse field driven Ising engine in presence of nonzero longitudinal field. We also numerically checked and found that the efficiency of such a (mixed) quantum Ising heat engine can indeed have much higher efficiency for appropriate values of the transverse and longitudinal fields.