A Coupled Quantum Otto Cycle
Quantum Physics
2015-05-20 v1 Mesoscale and Nanoscale Physics
Statistical Mechanics
Abstract
We study the 1-d isotropic Heisenberg model of two spin-1/2 systems as a quantum heat engine. The engine undergoes a four-step Otto cycle where the two adiabatic branches involve changing the external magnetic field at a fixed value of the coupling constant. We find conditions for the engine efficiency to be higher than the uncoupled model; in particular, we find an upper bound which is tighter than the Carnot bound. A new domain of parameter values is pointed out which was not feasible in the interaction-free model. Locally, each spin seems to effect the flow of heat in a direction opposite to the global temperature gradient. This seeming contradiction to the second law can be resolved in terms of local effective temperature of the spins.
Cite
@article{arxiv.1011.0815,
title = {A Coupled Quantum Otto Cycle},
author = {George Thomas and Ramandeep S. Johal},
journal= {arXiv preprint arXiv:1011.0815},
year = {2015}
}