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Quantum and classical Otto engine for a 2-D material: the case of a graphene quantum dot

In this work, we study the performance of classical and quantum magnetic Otto cycles with a working substance composed of a single graphene quantum dot modeled by the continuum approach with the use of the zigzag boundary condition. Modulating an external/perpendicular magnetic field, in the classical approach, we found a constant behavior in the total work extracted that is not present in the quantum formulation. We find that, in the classical approach, the engine yielded a greater performance in terms of total work extracted and efficiency as compared with its quantum counterpart. In the classical case, this is due to the working substance being in thermal equilibrium at each point of the cycle, maximizing the energy extracted in the adiabatic strokes.