Correlation Enhanced Autonomous Quantum Battery Charging via Structured Reservoirs

In this work, we investigate autonomous charging of a quantum battery coupled to a structured reservoir composed of two qubits, each locally coupled to its own bosonic thermal 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 reservoir qubits, charger, and battery, and (III) collective coupling between reservoir qubits and charger together with a local charger-battery interaction. Using incoherent and coherent initial states, we analyze stored energy, ergotropy, and charging power of the battery, and derive upper and lower bounds on extractable work in terms of 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 supporting the derived ergotropy bounds. Importantly, this work highlights how structured reservoirs enable autonomous and resource-enhanced quantum battery operation.