Controlling exciton dimensionality in novel transition-metal dichalcogenide platforms
type: CreativeWork
description: In this thesis, I control excitons in two-dimensional materials and explore their confinement across different dimensionality. I focus on transition-metal dichalcogenides (TMD), few-atom thick, layered materials, which are direct-bandgap semiconductors in the monolayer limit. These materials host excitons, bound electron-hole pairs, with large binding energies due to their two-dimensional nature. Broken inversion symmetry, along with strong spin-orbit interaction, leads to coupling of the spin and valley degrees of freedom, allowing for valley-selective optical transitions. First, I confine long-lived interlayer excitons in WSe2/WS2 heterobilayers to zero dimensions. Interlayer excitons have their electron and hole localised in separate TMD layers, providing extended optical lifetimes and a permanent electric dipole, opening the prospect of investigating long-ranged interactions in a many-body system. I find lifetimes approaching 0.2 ms for the unconfined excitons, longer by an order of magnitude than previous reports. I use an array of nanopillars to deterministically strain confine these interlayer excitons to zero dimensions and show them to have sufficiently long lifetime, up to ∼4 μs, to enable the investigation of quantum spin models. Next, I demonstrate one-dimensional electrical confinement of excitons in monolayer MoSe2. An in-plane electric field, combined with the creation of a lateral p-i-n junction, defines the confinement potential along an electrode edge. This leads to the emergence of quantised excitonic sub-bands, with magneto-optical measurements revealing the exchange-split linearly polarised fine structure of the exciton states. This system offers the possibility of electrically tuneable quantum confinement of excitons in an arbitrary geometry. Finally, I study excitonic complexes within two-dimensional Janus TMD monolayers. Here, an artificially altered atomic ordering breaks the out-of-plane mirror symmetry and creates an intrinsic electric fie…
abstract: In this thesis, I control excitons in two-dimensional materials and explore their confinement across different dimensionality. I focus on transition-metal dichalcogenides (TMD), few-atom thick, layered materials, which are direct-bandgap semiconductors in the monolayer limit. These materials host excitons, bound electron-hole pairs, with large binding energies due to their two-dimensional nature. Broken inversion symmetry, along with strong spin-orbit interaction, leads to coupling of the spin and valley degrees of freedom, allowing for valley-selective optical transitions. First, I confine long-lived interlayer excitons in WSe2/WS2 heterobilayers to zero dimensions. Interlayer excitons have their electron and hole localised in separate TMD layers, providing extended optical lifetimes and a permanent electric dipole, opening the prospect of investigating long-ranged interactions in a many-body system. I find lifetimes approaching 0.2 ms for the unconfined excitons, longer by an order of magnitude than previous reports. I use an array of nanopillars to deterministically strain confine these interlayer excitons to zero dimensions and show them to have sufficiently long lifetime, up to ∼4 μs, to enable the investigation of quantum spin models. Next, I demonstrate one-dimensional electrical confinement of excitons in monolayer MoSe2. An in-plane electric field, combined with the creation of a lateral p-i-n junction, defines the confinement potential along an electrode edge. This leads to the emergence of quantised excitonic sub-bands, with magneto-optical measurements revealing the exchange-split linearly polarised fine structure of the exciton states. This system offers the possibility of electrically tuneable quantum confinement of excitons in an arbitrary geometry. Finally, I study excitonic complexes within two-dimensional Janus TMD monolayers. Here, an artificially altered atomic ordering breaks the out-of-plane mirror symmetry and creates an intrinsic electric fie…
author: Feuer, Matthew
language: eng
keywords: 2D materials, Excitons, Quantum, Quantum optics, TMD, Transition-metal dichalcogenides
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/65cd5d77-e4c0-4b00-8c1a-a3bc28047e5b/download
license: https://creativecommons.org/licenses/by/4.0/
date published: 2023-05-01
date modified: 2026-07-22T22:24:31Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.104224