Quantum thermal machine regimes in the transverse-field Ising model

TL;DR

This paper explores how a transverse-field Ising model can function as a quantum thermal machine, identifying regimes like heat engine, refrigerator, and heater based on equilibrium properties and many-body quantum effects.

Contribution

It introduces a method to analyze quantum thermal machine regimes in many-body systems using infinitesimal work strokes and equilibrium properties, extending understanding beyond simple models.

Findings

Infinitesimal work strokes enable heat engine and accelerator regimes.

Operation boundaries are described by macroscopic properties like net transverse magnetization.

Regimes at low temperatures are understood via quasiparticles, high temperatures via free energy expansion.

Abstract

We identify and interpret the possible quantum thermal machine regimes with a transverse-field Ising model as the working substance. In general, understanding the emergence of such regimes in a many-body quantum system is challenging due to the dependence on the many energy levels in the system. By considering infinitesimal work strokes, we can understand the operation from equilibrium properties of the system. We find that infinitesimal work strokes enable both heat engine and accelerator operation, with the output and boundaries of operation described by macroscopic properties of the system, in particular the net transverse magnetization. At low temperatures, the regimes of operation and performance can be understood from quasiparticles in the system, while at high temperatures an expansion of the free energy in powers of inverse temperature describes the operation. The understanding generalises to larger work strokes when the temperature difference between the hot and cold reservoirs is large. For hot and cold reservoirs close in temperature, a sufficiently large work stroke can enable refrigerator and heater regimes. Our results and method of analysis will prove useful in understanding the possible regimes of operation of quantum many-body thermal machines more generally.