  We design a quantum spin heat engine using spin polarized ballistic modes
generated in a strained graphene monolayer doped with a magnetic impurity. We
observe remarkably large efficiency and large thermoelectric figure of merit
both for the charge as well as spin variants of the quantum heat engine. This
suggests the use of this device as a highly efficient quantum heat engine for
charge as well as spin-based transport. Further, a comparison is drawn between
the device characteristics of a graphene spin heat engine against a quantum
spin Hall heat engine. The reason being edge modes because of their origin
should give much better performance. In this respect, we observe our
graphene-based spin heat engine can almost match the performance
characteristics of a quantum spin Hall heat engine. Finally, we show that a
pure spin current can be transported in our device in absence of any charge
current.
