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Title: Topological insulator nanoparticles and their photonic analogues
Author: Siroki, Gleb
ISNI:       0000 0004 7658 329X
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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The exploration of topological insulators has been a remarkable success of band theory. Topological insulators are distinguished from ordinary ones by the boundary states which exist at the edge of those materials and are robust against disorder. Moreover, for these states the propagation direction depends on the spin in the absence of time-reversal breaking. This makes topological insulators promising candidates for spintronics as well as some optical applications. Because the their unique properties from single-particle band structure the analogous topological phases also exist for photons. Photonic crystals displaying topological properties promise to deliver waveguides where light can be guided without scattering and its direction { controlled by polarization. Following the drive for miniaturization one would like to make use of the described effects at the smallest scale possible. This conserves energy as well as materials and serves as the main motivation for the current work. The properties of boundary states have been largely explored in infinite (macroscopic) samples but not in finite ones. In the first half of this thesis we study quantum-confined topological nanoparticles. In particular, we use the tight-binding method to show that discrete surface states in the nanoparticles have the same protection from disorder as continuous bands in macroscopic samples. In addition, we analytically show that the surface states strongly affect the optical properties of such nanoparticles compared with those made from ordinary insulators. The second part of this thesis is devoted to topological photonics. Here we show both analytically and with numerical simulations that confined samples of photonic topological insulators have edge states supporting unidirectional propagation. Furthermore, we explore two designs - a 3D crystal and a 2D metasurface, which display topological properties and have not received any attention in the literature so far.
Supervisor: Giannini, Vincenzo ; Lee, Derek ; Haynes, Peter Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral