# Quantum supercapacitors

## TL;DR

This paper introduces a quantum supercapacitor model using coupled quantum dot chains in a photonic cavity, revealing phase transitions that significantly enhance quantum capacitance and energy storage potential.

## Contribution

It presents a novel theoretical model of a quantum supercapacitor with phase diagram analysis, highlighting quantum effects that boost capacitance beyond classical limits.

## Key findings

- Identification of ferromagnetic, antiferromagnetic, and superradiant phases.
- Quantum capacitance is greatly enhanced during phase transitions.
- Potential for experimental realization of quantum supercapacitors.

## Abstract

Recently there has been a great deal of interest on the possibility to exploit quantum-mechanical effects to increase the performance of energy storage systems. Here we introduce and solve a model of a quantum supercapacitor. This consists of two chains, one containing electrons and the other one holes, hosted by arrays of double quantum dots, the latter being a building block of experimental architectures for realizing charge and spin qubits. The two chains are in close proximity and embedded in the same photonic cavity, which is responsible for long-range coupling between all the qubits, in the same spirit of the Dicke model. By employing a variational approach, we find the phase diagram of the model, which displays ferromagnetic and antiferromagnetic phases for suitable pseudospin degrees of freedom, together with phases characterized by collective superradiant behavior. Importantly, we show that when transitioning from the ferro/antiferromagnetic to the superradiant phase, the quantum capacitance of the model is greatly enhanced. Our work offers opportunities for the experimental realization of a novel class of quantum supercapacitors with an enhanced storing power stemming from exquisite quantum mechanical effects.