Implementation of a quantum Otto thermal machine using an XX spin chain model

Abstract

Quantum thermal machine models are essential to understanding the thermodynamics of nanoscale systems. A quantum Otto thermal machine with a spin XX chain working substance was considered. The different working regimes was demonstrated for a chain of ten spins by calculating the work and heat absorbed for one cycle. It was found that at high bath temperatures, the quantum Otto engine mainly operates as either accelerator or a heat engine, while at low bath temperatures it operates mainly as a heater. Additionally, sinusoidal fluctuations in the heat and work plots are more apparent at low bath temperatures. This is presumably attributed to the low dimension of the system, which dissappears in the thermodynamic limit. These findings are precursor to optimal device design using Otto engines based on the spin XX chain model.