In the abstract of [Phys. Rev. Lett. 125, 040601 (2020)] one can read that “[$\dots$] to have a nonzero rate of change of the extractable work, the state ${\rho }_{\mathcal{W}}$ of the battery cannot be an eigenstate of a ‘free energy operator,’ defined by $\mathcal{F}\equiv H_{\mathcal{W}}+{\beta }^{-1}\log ({\rho }_{\mathcal{W}})$, where $H_{\mathcal{W}}$ is the Hamiltonian of the battery and $\beta$ is the inverse temperature [$\dots$].” Contrarily to what is presented below Eq. (17) of the Letter, we observe that the above conclusion does not hold when the battery is subject to nonunitary dynamics.

• Received 15 December 2020
• Accepted 4 June 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.028901