Summary: | We study the impact of cooperative many-body effects on the operation of periodically-driven quantum thermal machines, particularly heat engines and refrigerators. In suitable geometries, N two-level atoms can exchange energy with the driving field and the (hot and cold) thermal baths at a faster rate than a single atom due to their SU(2) symmetry that causes the atoms to behave as a collective spin- N /2 particle. This cooperative effect boosts the power output of heat engines compared to the power output of N independent, incoherent, heat engines. In the refrigeration regime, similar cooling-power boost takes place.
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