High-efficiency three-stroke quantum isochoric heat engine: From infinite potential wells to magic-angle twisted bilayer graphene.

We introduce a three-stroke quantum isochoric cycle that functions as a heat engine operating between two thermal reservoirs. Implemented for a particle confined in a one-dimensional infinite potential well, the cycle's performance is benchmarked against the classical three-stroke triangular and isochoric engines. We find that the quantum isochoric cycle achieves a higher efficiency than both classical counterparts and also surpasses the efficiency of the recently proposed three-stroke quantum isoenergetic cycle. Owing to its reduced number of strokes, the design substantially lowers control complexity in nanoscale thermodynamic devices, offering a more feasible route to experimental realization compared to conventional four-stroke architectures. We further evaluate the cycle in graphene-based systems under an external magnetic field, including monolayer graphene, AB-stacked bilayer graphene, and twisted bilayer graphene at both magic and nonmagic twist angles. Among these platforms, magic-angle twisted bilayer graphene attains the highest efficiency at fixed work output, highlighting its promise for quantum thermodynamic applications.