Designing robust quantum refrigerators in disordered spin models

We explore a small quantum refrigerator in which the working substance is made of paradigmatic nearestneighbor quantum spin models, the XY Z 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 degrading, 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 merit by using global master equations.

Automated summary

This study explores a small quantum refrigerator using XY Z and XY models as the working substance. Within a certain range of interaction strengths, the cooling effect of the selected spin can be ensured by appropriate tuning. The experimental results show that when one of the interaction strengths is disordered, the performance of the refrigerator remains unchanged. However, to achieve significant cooling effects, it is necessary to go beyond the weak-coupling limit and compute the figures of merit using global master equations.