  A two-terminal quantum spin-Hall heat engine and refrigerator with embedded
Majorana bound states (MBS) are analyzed for optimality in thermoelectric
performance. The occurrence of MBS can enhance the performance to rival, as
well as outperform, some modern nanoscale quantum heat engines and quantum
refrigerators. The optimal performance of this MBS quantum heat engine and
quantum refrigerator can be further enhanced by an Aharonov-Bohm flux.
