Designing Robust Quantum Refrigerators in Disordered Spin Models

TL;DR

This paper investigates the design of quantum refrigerators using disordered and ordered spin models, demonstrating robustness to disorder and the importance of beyond weak-coupling analysis for effective cooling.

Contribution

It introduces a quantum refrigerator model based on spin chains with disorder, showing robustness and the necessity of global master equations for strong coupling regimes.

Findings

Performance remains stable under disorder in interaction strengths.

Weak-coupling limit suffices for initial cooling analysis.

Beyond weak-coupling, global master equations are needed for accurate figures of merit.

Abstract

We explore a small quantum refrigerator in which the working substance is made of paradigmatic nearest-neighbor quantum spin models, the XYZ and the XY model with Dzyaloshinskii-Moriya interactions, consisting of two and three spins, each of which is in contact with a bosonic bath. We identify a specific range of interaction strengths which can be tuned appropriately to ensure a cooling of the selected spin in terms of its local temperature in the weak-coupling limit. Moreover, we report that in this domain, when one of the interaction strengths is disordered, the performance of the thermal machine operating as a refrigerator remains almost unchanged instead of degradation, thereby establishing the flexibility of this device. However, to obtain a significant amount of cooling via ordered as well as disordered spin models, we observe that one has to go beyond the weak-coupling limit and compute the figures of merits by using global master equations.