D. M. Rouse | Searcharxiv

arXiv2022

Superabsorption in an organic microcavity: towards a quantum battery

The rate at which matter emits or absorbs light can be modified by its environment, as dramatically exemplified by the widely-studied phenomenon of superradiance. The reverse process, superabsorption, is harder to demonstrate due to the challenges of probing ultrafast processes, and has only been seen for small numbers of atoms. Its central idea - superextensive scaling of absorption meaning larger systems absorb faster - is also the key idea underpinning quantum batteries. Here we implement experimentally a paradigmatic model of a quantum battery, constructed of a microcavity enclosing a molecular dye. Ultrafast optical spectroscopy allows us to observe charging dynamics at femtosecond resolution to demonstrate superextensive charging rates and storage capacity, in agreement with our theoretical modelling. We find that decoherence plays an important role in stabilising energy storage. Our work opens new opportunities for harnessing collective effects in light-matter coupling for nanoscale energy capture, storage, and transport technologies.

quant-ph↗

arXiv2019

Optimal power generation using dark states in dimers strongly coupled to their environment

Dark state protection has been proposed as a mechanism to increase the power output of light harvesting devices by reducing the rate of radiative recombination. Indeed many theoretical studies have reported increased power outputs in dimer systems which use quantum interference to generate dark states. These models have typically been restricted to particular geometries and to weakly coupled vibrational baths. Here we consider the experimentally-relevant strong vibrational coupling regime with no geometric restrictions on the dimer. We analyze how dark states can be formed in the dimer by numerically minimizing the emission rate of the lowest energy excited eigenstate, and then calculate the power output of the molecules with these dark states. We find that there are two distinct types of dark states depending on whether the monomers form homodimers, where energy splittings and dipole strengths are identical, or heterodimers, where there is some difference. Homodimers, which exploit destructive quantum interference, produce high power outputs but strong phonon couplings and perturbations from ideal geometries are extremely detrimental. Heterodimers, which are closer to the classical picture of a distinct donor and acceptor molecule, produce an intermediate power output that is relatively stable to these changes. The strong vibrational couplings typically found in organic molecules will suppress destructive interference and thus favour the dark-state enhancement offered by heterodimers.

quant-ph↗