Correlation Enhanced Autonomous Quantum Battery Charging via Structured Reservoirs

In this work, we investigate the autonomous charging process of a quantum battery coupled to a structured reservoir composed of two qubits, each in thermal equilibrium with its own bosonic bath. Moreover, the reservoir interacts with a charger-battery architecture through three configurations: (I) direct coupling between reservoir qubits and battery, (II) collective coupling among the reservoir qubits, charger, and battery, while (III) reflects a collective coupling between the reservoir qubits and charger together with a local charger-battery interaction. However, by using incoherent and coherent initial states, we analyze the stored energy, ergotropy, and charging power of battery, where we derive the upper and lower bounds on the extractable work in terms of the free energy of coherence and correlations exchanged between subsystems. Our results show that global and local coherences, as well as total correlations act as quantum resources that enhance autonomous charging. Additionally, we demonstrate that the free energy stored in the quantum battery splits into contributions from coherence and correlations, providing numerical evidence that supports the derived ergotropy bounds. Importantly, this work highlights how structured reservoirs enable autonomous and resource-enhanced quantum battery operation.