Optimal Performance of an Asymmetric Quantum Harmonic Otto Engine and Refrigerator

Abstract: We study a quantum Otto cycle operating with a time-dependent harmonic oscillator as the working material. We examine the asymmetry present between the two adiabatic processes of the Otto cycle, focusing on cases of sudden expansion and sudden compression. We analytically derive the efficiency and coefficient of performance for an asymmetric Otto cycle, employing the Omega function, which represents the balance between the maximum useful energy and minimum lost energy. Notably, our findings reveal that the efficiency (coefficient of performance) of an asymmetric engine (refrigerator) is higher during the sudden compression case compared to the sudden expansion case. Furthermore, we derive the results for the maximum work efficiency and observe that efficiency at the maximum Omega function consistently exceeds the maximum work efficiency. Finally, we compute the fractional loss of work in both cases to thoroughly examine the performance of asymmetric Otto engine.