  This study examines the performance of finite spin quantum batteries (QBs)
using Heisenberg spin models with Dzyaloshinsky-Moriya (DM) and
Kaplan--Shekhtman--Entin-Wohlman--Aharony (KSEA) interactions. The QBs are
modeled as interacting quantum spins in local inhomogeneous magnetic fields,
inducing variable Zeeman splitting. We derive analytical expressions for the
maximal extractable work, ergotropy and the capacity of QBs, as recently
examined by Yang et al. [Phys. Rev. Lett. 131, 030402 (2023)]. These quantities
are analytically linked through certain quantum correlations, as posited in the
aforementioned study. Different Heisenberg spin chain models exhibit distinct
behaviors under varying conditions, emphasizing the importance of model
selection for optimizing QB performance. In antiferromagnetic (AFM) systems,
maximum ergotropy occurs with a Zeeman splitting field applied to either spin,
while ferromagnetic (FM) systems benefit from a uniform Zeeman field.
Temperature significantly impacts QB performance, with ergotropy in the AFM
case being generally more robust against temperature increases compared to the
FM case. Incorporating DM and KSEA couplings can significantly enhance the
capacity and ergotropy extraction of QBs. However, there exists a threshold
beyond which additional increases in these interactions cause a sharp decline
in capacity and ergotropy. This behavior is influenced by temperature and
quantum coherence, which signal the occurrence of a sudden phase transition.
The resource theory of quantum coherence proposed by Baumgratz et al. [Phys.
Rev. Lett. 113, 140401 (2014)] plays a crucial role in enhancing ergotropy and
capacity. However, ergotropy is limited by both the system's capacity and the
amount of coherence. These findings support the theoretical framework of
spin-based QBs and may benefit future research on quantum energy storage
devices.
