Comparing different operating regimes of a Dicke quantum battery

In this paper, we consider a quantum battery, namely a miniaturized device able to store energy and release it on-demand. In the so-called Dicke configuration, it is made of N two-level systems embedded into a cavity which plays the role of charger. In this context, we compare two different situations, namely: the resonant regime, where the energy of the two-level systems is the same as the one of the photons trapped in the cavity, and the off-resonant regime, where the photons are way more energetic. We observe that, while the energy stored per two-level system is comparable in the two cases, the average charging power, despite showing the same asymptotic superextensive scaling, is strongly suppressed in the latter. This analysis will help to orient future experimental implementations of these devices.