Quantum Otto heat-engine with Kitaev-Heisenberg cluster: Possible roles of frustration, magnons, and duality

TL;DR

This paper investigates the efficiency of a quantum Otto engine using Kitaev-Heisenberg clusters, highlighting the roles of frustration, magnons, and duality, and demonstrating quantum advantages in certain spin systems.

Contribution

It introduces a detailed analysis of KH clusters as quantum engine media, revealing how frustration and duality influence efficiency and identifying conditions for quantum advantage.

Findings

Efficiency depends on Kitaev and Heisenberg interactions.

Maximum efficiency relates to eigen-spectra forming narrow bands.

Quantum advantage observed for spin-1/2 systems.

Abstract

We study the performance of Kitaev-Heisenberg (KH) clusters as working media realizing a quantum Otto engine (QOE). An external Zeeman field with linear time dependency is used as the driving mechanism. The efficiency strongly depends on Kitaev ($\kappa$) and Heisenberg ($J$) exchange interaction. Interestingly, efficiency is comparable when the relative magnitude of $\kappa$ and $J$ is the same but of opposite signs. The above results are explained due to a subtle interplay of frustration, quantum fluctuation, and duality of eigen-spectra for the KH system when both the signs of $\kappa$ and $J$ are reversed. The maximum efficiency is shown to be dynamically related to eigen-spectra forming discrete narrow bands, where total spin angular momentum becomes a good quantum number. We relate this optimum efficiency to the realization of weakly interacting magnons, where the system reduces to an approximate eigen-system of the external drive. Finally, we extend our study to the large spin Kitaev model and find a quantum advantage in efficiency for $S=1/2$. The results could be of practical interest for materials with KH interactions as a platform for QOE.