Superradiance and Superabsorption Engine of $N$ Two-Level Systems: $N^2$-Power Scaling at Near-Unity Efficiency

We present a thermal engine that exploits the \emph{cooperative superradiance} and \emph{superabsorption} of a sample of $N$ two-level atoms. This engine operates using a single cold reservoir via cycles of collective pumping followed by decay. Using an effective mean-field Hamiltonian to describe the many-body dynamics, we design optimized drive pulses that preserve adiabaticity and achieve an average power output scaling quadratically with the system size, $P\propto N^2$. An experimentally measurable figure of merit demonstrates that the efficiency of this superengine can approach unity. The resulting analytical model, which yields a representative Hamiltonian for the sample within the mean-field formalism, is validated by numerical simulations. Our results pave the way for scalable and highly efficient quantum heat engines based on collective effects.