The influence of environments on energy transfer

Waller, Madeline Claire (2025) The influence of environments on energy transfer. PhD thesis, University of Glasgow.

Abstract

Energy transfer between atoms/molecules, one of the most basic interactions within atomic and molecular systems, is important in many diverse areas of science. The ability to control these processes is therefore a powerful tool with applications in various fields, and one method to achieve this influence is through the use of macroscopic bodies. Making use of the theoretical framework of macroscopic quantum electrodynamics (QED), the environment of a microscopic system can be introduced into the quantum description, and its influence on intermolecular energy transfer can be characterized. In this work, we explore the ways in which intermolecular interactions can be impacted by a macroscopic environment. We derive a general expression for the rate of resonant energy transfer (RET) between a donor and an acceptor in an arbitrary, reciprocal environment and examine how the medium’s properties and the molecular positions affect the interaction rate. Our consideration is then extended to include non-reciprocal media, again calculating a general expression for the energy transfer rate and applying to a simple setup containing non-reciprocal media. In particular, we investigate how the properties of the medium can be altered to promote unidirectional energy propagation. We will also explore an application of this principle, which makes use of inverse design in the creation of an optical isolator. In real-world situations, a donor and acceptor can also be coupled to additional interacting bodies as well as their environment, and these can have an intricate impact on the rate of energy transfer between them. The introduction of a third molecule significantly complicates the calculation of the rate, so in this work we use canonical transformations to reduce this computational complexity and derive a general expression for the rate of three-body RET in a macroscopic background. Applying this to some simple setups demonstrates the distinctive effect the mediating body can have. Finally, we investigate how a macroscopic body can be used to induce a superabsorbing state in a system of dipoles via control of the intermolecular coupling. After a demonstration of this principle for a simple model system, we consider a ring of optical dipoles, inspired by naturally occurring photosynthetic systems. We demonstrate how the placement of a macroscopic sphere inside the ring can produce superabsorption in the system, making it suitable for use in artificial light harvesting and showing performance superior to previous methods.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Funder's Name: Engineering and Physical Sciences Research Council (EPSRC)
• Supervisor's Name: Bennett, Dr. Robert and Barnett, Professor Stephen
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85195
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 16 Jun 2025 07:54
• Last Modified: 16 Jun 2025 07:58
• Thesis DOI: 10.5525/gla.thesis.85195
• URI: https://theses.gla.ac.uk/id/eprint/85195

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