Dephasing-powered open quantum-dot battery

Abstract

We propose a simple realization of an open quantum battery powered by local dephasing. The setup consists of a triple-quantum-dot chain coupled at one end to a thermal reservoir, with the dot at the opposite end strongly detuned to form a high-energy storage element. Local dephasing populates this highly excited state and autonomously drives the system into a nonequilibrium steady state with high ergotropic efficiency. We find a limit where the ergotropic efficiency approaches unity, while the ergotropy itself approaches one-third of the energy detuning. We characterize the battery through its energy-storage performance, charging time, and stability, showing that the charged state remains long-lived after the dephasing source is switched off. We then demonstrate two complementary protocols for extracting the stored energy. First, nearly all the available ergotropy can be recovered through a simple cyclic unitary protocol involving only modulation of the detuned-dot gate. Second, coupling the detuned dot to an electronic load allows the extraction of electrochemical work exceeding the initial ergotropy, thereby accessing part of the battery's passive energy. Our results establish local dephasing as an autonomous resource for charging open quantum batteries and demonstrate simple routes for extracting the resulting stored energy in experimentally accessible mesoscopic platforms.

The paper asks whether local dephasing can charge an open quantum-dot battery and how the stored energy can subsequently be extracted. It considers a triple-dot chain in strong Coulomb blockade, with at most one electron, a strongly detuned storage dot at one end, and a thermal electron reservoir at the other. Dephasing transfers population into the high-energy eigenstate, whose weak reservoir overlap suppresses leakage. Global reservoir Lindblad dynamics combined with local dephasing are studied numerically and analytically at large detuning. The leading-order ergotropic fraction is $\mathcal W_{\rm ss}/E_{\rm ss}\simeq\tanh(\Omega/k_{\rm B}T)$; at low temperature it approaches unity, with ergotropy approaching $\Delta/3$. For $\Delta=100\Omega$, $\gamma=10\Omega$, $\Gamma=0.1\Omega$, and $k_{\rm B}T=\Omega$, simulations give $E_{\rm ss}\simeq27.76\Omega$ and $\mathcal W_{\rm ss}\simeq20.17\Omega$. Charging time scales as $\hbar\Delta^2/(\gamma\Omega^2)$, while reservoir leakage scales as $\Gamma\Omega^4/(\hbar\Delta^4)$. A numerically selected cyclic storage-dot gate protocol extracts approximately $98.6\%$ of the initial ergotropy. Alternatively, coupling the storage dot to an electronic load converts energy into electrochemical work and can exceed the initial ergotropy through nonunitary particle exchange. The model assumes weak reservoir coupling, Markovian noise, and single-orbital dynamics. Resistor-noise and biased-detector implementations require sufficiently broadband fluctuations; the former requires a noise temperature well above $\Delta/k_{\rm B}$. The ergotropic fraction is not an overall charging efficiency. Phonon relaxation is treated phenomenologically, so actual storage lifetimes remain device-dependent. Capacity scaling beyond the single-electron unit is left open.