Two-mode Raman quantum battery dependent on coupling strength

We investigate a series of two-mode quantum batteries (QBs) which exhibits better performance in both the stored energy and average charging power compared to the two-photon case. In both the model related to coupling strength and Raman cases, we find the QBs can store energy faster and have a higher efficiency than the original case. Among the derived models we have studied, the two-mode Raman QB dependent on coupling strength has the best performance. We also present the relationship between the ergotropy and battery-charger entanglement of incoherent QBs and define the resource utilization efficiency k(t) and kins(t). We find that entanglement in the energy-extraction stage is a key resource. In addition, we consider a collection of two-level systems embedded in a two-mode microwave cavity with counterrotating terms, which shows that the counterrotating terms lead to a higher stored energy in the ultrastrong-coupling regime.