Topological physics in one-dimensional chains of metallic nanoparticles
File(s)
Author(s)
Pocock, Simon
Type
Thesis
Abstract
The focus of this thesis is the study of a chain of metal nanoparticles with alternating spacing, an artistic impression of which is given in figure 0.1. At first glance, this seems like a fairly simple system but, in reality, its study is a dive into two of the most exciting fields in modern condensed matter physics: topological insulators and light-matter interactions. In fact, the properties of light lead us to consider some of the most pressing questions in the field of topological insulators today.
The first half of the thesis covers all of the theory needed to understand the original work presented in the second half. The first chapter includes a historical review of topological insulators, an introduction to some of the fundamental concepts in the field, and an overview of photonic and non-Hermitian topological insulators. This is followed, in the second chapter, by a detailed discussion of the famous Su-Schrieffer-Heeger model and important results from the theory of scattering of light by nanoparticles.
In the remaining chapters, which make up the second half of the thesis, we present models for the chain which take into account the nature of light and result in a wealth of interesting topological physics. The polarisation of light affects the topology dramatically, with stable topology and protected plasmonic edge states in one polarisation and the complete breakdown of bulk-edge correspondence in another. The absorption of light and its phase properties force the system to be non-Hermitian. This, combined with the long range coupling of the metal nanoparticles, leads to unexpected topological phase transitions. These results are elaborated on in the following work, along with extinction cross sections of the chain, a non-Hermitian next-nearest-neighbour Su-Schrieffer-Heeger model extension, and a minimal model for the non-Hermitian phase transitions.
The first half of the thesis covers all of the theory needed to understand the original work presented in the second half. The first chapter includes a historical review of topological insulators, an introduction to some of the fundamental concepts in the field, and an overview of photonic and non-Hermitian topological insulators. This is followed, in the second chapter, by a detailed discussion of the famous Su-Schrieffer-Heeger model and important results from the theory of scattering of light by nanoparticles.
In the remaining chapters, which make up the second half of the thesis, we present models for the chain which take into account the nature of light and result in a wealth of interesting topological physics. The polarisation of light affects the topology dramatically, with stable topology and protected plasmonic edge states in one polarisation and the complete breakdown of bulk-edge correspondence in another. The absorption of light and its phase properties force the system to be non-Hermitian. This, combined with the long range coupling of the metal nanoparticles, leads to unexpected topological phase transitions. These results are elaborated on in the following work, along with extinction cross sections of the chain, a non-Hermitian next-nearest-neighbour Su-Schrieffer-Heeger model extension, and a minimal model for the non-Hermitian phase transitions.
Version
Open Access
Date Issued
2019-11
Date Awarded
2020-03
Copyright Statement
Creative Commons Attribution NonCommercial Licence
Advisor
Giannini, Vincenzo
Lee, Derek
Sponsor
Engineering and Physical Sciences Research Council
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)