arXiv subjects

Erik M Gauger

Publications and source records attributed to Erik M Gauger.

5 recordsLinked to original sources

arXiv2024

Influence of strong molecular vibrations on decoherence of molecular polaritons

We derive the transition rates, dephasing rates, and Lamb shifts for a system consisting of many molecules collectively coupled to a resonant cavity mode. Using a variational polaron master equation, we show that strong vibrational interactions inherent to molecules give rise to multi phonon processes and suppress the light--matter coupling. In the strong light--matter coupling limit, multi-phonon contributions to the transition and dephasing rates strongly dominate over single phonon contributions for typical molecular parameters. This leads to novel dependencies of the rates and spectral line widths on the number of molecules in the cavity. We also find that vibrational Lamb shifts can substantially modify the polariton energies in the strong light--matter coupling limit.

quant-ph↗

arXiv2023

Light-harvesting efficiency cannot depend on optical coherence in the absence of orientational order

The coherence of light has been proposed as a quantum-mechanical control for enhancing light-harvesting efficiency. In particular, optical coherence can be manipulated by changing either the polarization state or spectral phase of the light. Here, we show that, in weak light, light-harvesting efficiency cannot be controlled using any form of optical coherence in molecular light-harvesting systems and, more broadly, those comprising orientationally disordered sub-units and operating on longer-than-ultrafast timescales. Under those conditions, optical coherence does not affect light-harvesting efficiency, meaning that it cannot be used for control. Specifically, polarization-state control is lost in disordered samples or when the molecules reorient on the timescales of the light-harvesting, and spectral-phase control is lost when the efficiency is time-averaged for longer than the optical coherence time. In practice, efficiency is always averaged over long times, meaning that coherent optical control is only possible through polarisation in systems with orientational order.

physics.chem-ph↗

arXiv2023

From Goldilocks to Twin Peaks: multiple optimal regimes for quantum transport in disordered networks

Understanding energy transport in quantum systems is crucial for an understanding of light-harvesting in nature, and for the creation of new quantum technologies. Open quantum systems theory has been successfully applied to predict the existence of environmental noise-assisted quantum transport (ENAQT) as a widespread phenomenon occurring in biological and artificial systems. That work has been primarily focused on several `canonical' structures, from simple chains, rings and crystals of varying dimensions, to well-studied light-harvesting complexes. Studying those particular systems has produced specific assumptions about ENAQT, including the notion of a single, ideal, range of environmental coupling rates that improve energy transport. In this paper we show that a consistent subset of physically modelled transport networks can have at least two ENAQT peaks in their steady state transport efficiency.

quant-ph↗

arXiv2021

An analytic expression for the optical exciton transition rates in the polaron frame

When an optical emitter is strongly coupled to a vibrational bath the polaron transformation is often used to permit an accurate second-order Redfield master equation. However, the optical transition rates in the polaron frame are not analytic and approximations typically need to be made which result in the loss of anything other than simple additive effects of the two baths. In this paper, we derive an intuitive analytic expression for the polaron frame optical transition rates by means of a finite mode truncation of the vibrational bath. Using this technique, calculations of the transition rates converge for only a few modes in the truncated spectral density, and capture non-additive effects such as population inversion of a two-level system.

quant-ph↗

arXiv2012

A new model for magnetoreception

Certain migratory birds can sense the earth's magnetic field. The nature of this process is not yet properly understood. Here we offer a simple explanation according to which birds literally `see' the local magnetic field: Our model relates the well-established radical pair hypothesis to the phenomenon of Haidinger's brush, a capacity to see the polarisation of light. This new picture explains recent surprising experimental data indicating long lifetimes for the radical pair. Moreover there is a clear evolutionary path toward this field sensing mechanism: it is an enhancement of a weak effect that may be present in many species.

physics.bio-ph↗