Comparison of the coupled quantum Carnot and Otto cycles

We propose two coupled spins 1/2 interacting via Lipkin-Meshkov-Glick or Heisenberg XXX model as the working substance of either the quantum Carnot engine or the quantum Otto engine cycles. We compare and contrast the performance outputs of the quantum Carnot and Otto cycles under the same condition. The benefit of the use of a coupled quantum working substance on the performance of a quantum heat engine is also revealed. The harvested work in the cycles are found to be remarkably increased by the quantum interaction between the spins. The quantum Carnot cycle produces more work than that of the Otto cycle. On the other hand, when the ratio between the work obtained from the coupled spins and the one from the uncoupled spins is compared, the Otto cycle is found to be more capable than the Carnot cycle to enhance the net work output. (C) 2019 Elsevier B.V. All rights reserved.