Photons in a twisted lattice
(2024) PHYM01 20232Mathematical Physics
Department of Physics
- Abstract
- In this thesis, a finite square Moiré system placed inside an optical cavity was simulated. Two commensurate angles, θ = 0 and θ ≈ 37 were considered. The fluorescence spectrum was obtained for both angles and for systems with one particle or two particles with opposite spin. The twisted configuration was found to have a richer fluorescence structure compared to the aligned configuration, which exhibited a rather simple and trivial spectrum. Including interactions was found to reduce the signal in the twisted configuration while having little effect on the aligned configuration. For a time-dependent angle, the energy added from the switching itself dominated the spectrum and became essentially independent of the incident frequency. The... (More)
- In this thesis, a finite square Moiré system placed inside an optical cavity was simulated. Two commensurate angles, θ = 0 and θ ≈ 37 were considered. The fluorescence spectrum was obtained for both angles and for systems with one particle or two particles with opposite spin. The twisted configuration was found to have a richer fluorescence structure compared to the aligned configuration, which exhibited a rather simple and trivial spectrum. Including interactions was found to reduce the signal in the twisted configuration while having little effect on the aligned configuration. For a time-dependent angle, the energy added from the switching itself dominated the spectrum and became essentially independent of the incident frequency. The numerical and exploratory nature of this thesis leaves many questions unanswered and opens the way for more in depth investigations both at the theoretical and computational level. (Less)
- Popular Abstract
- Have you ever wondered why you never see somebody with a striped shirt on TV? Probably not, but let me tell you why. It is because of a phenomena called Moir´e patterns and they make striped shirts unbearable too look at through a TV screen. However, the nuisance of the cameraman has recently been making waves in the physics community. Strange things seem to happen when these patterns arise in crystals. In this thesis, we explore how 2D Moir´e crystals interact with light.
When two periodic structures, for example the stripes on a shirt and lines of pixels on a TV screen are overlaid, they can create so called Moir´e patterns. A Moir´e material then forms when these patterns arise in materials. These are particularly prevalent in the... (More) - Have you ever wondered why you never see somebody with a striped shirt on TV? Probably not, but let me tell you why. It is because of a phenomena called Moir´e patterns and they make striped shirts unbearable too look at through a TV screen. However, the nuisance of the cameraman has recently been making waves in the physics community. Strange things seem to happen when these patterns arise in crystals. In this thesis, we explore how 2D Moir´e crystals interact with light.
When two periodic structures, for example the stripes on a shirt and lines of pixels on a TV screen are overlaid, they can create so called Moir´e patterns. A Moir´e material then forms when these patterns arise in materials. These are particularly prevalent in the world of 2D crystals. A 2D crystal is like a grid where each intersection represents an atom. The electron, from which all the fun physics emerges from, jump around in this grid along the grid lines. Introducing a second grid and bringing it close, the electrons can also start to jump between the two grids. If we now twist the grids and look from above, we will see that we have created a Moir´e pattern. At certain angles these patterns become repeating, which is especially nice for creating interesting physics. When the grids are twisted the electrons will not be as free to jump between the two grids. Instead, only certain points of the grid which align will work as bridges between them.
Much of the properties of solid materials are grounded in the geometric structure and periodicity of the atomic grids. The introduction of the Moir´e pattern changes this periodicity and much of the properties with it. These systems have been shown especially prone to correlated electrons. Correlated essentially means that the whole is greater than the sum of it’s part. This is the heart of Quantum Mechanics and there is great hope in the possibility of harnessing the power of these correlations, for example in quantum computers.
In this thesis a Moir´e system is explored with a focus on how it interacts with light. We consider a special angle where a certain Moir´e pattern arises and compare it to when there is no twist between the layers. The twist creates a rich landscape of interactions with light compared to the basic interactions in the no twist system. By switching between the two angles dynamically, we find that the interactions are dominated by the energy that is added to the system when switching the angle. We also investigated what would happen to the system if there were two electrons jumping around in it. Electrons are negatively charged and therefore try to avoid each other. It was found that the interaction with light was unaffected in the aligned system when we had two electrons hiding from each other. However, the twisted system, containing the Moir´e pattern, the interaction with light was reduced as an effect of this electron hiding (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9169318
- author
- Kärrholm, Gustav LU
- supervisor
- organization
- course
- PHYM01 20232
- year
- 2024
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Moiré, Fluorescence, Exact diagonalization, Time evolution, Optical cavity
- language
- English
- id
- 9169318
- date added to LUP
- 2024-07-03 15:21:59
- date last changed
- 2024-07-03 15:21:59
@misc{9169318,
abstract = {{In this thesis, a finite square Moiré system placed inside an optical cavity was simulated. Two commensurate angles, θ = 0 and θ ≈ 37 were considered. The fluorescence spectrum was obtained for both angles and for systems with one particle or two particles with opposite spin. The twisted configuration was found to have a richer fluorescence structure compared to the aligned configuration, which exhibited a rather simple and trivial spectrum. Including interactions was found to reduce the signal in the twisted configuration while having little effect on the aligned configuration. For a time-dependent angle, the energy added from the switching itself dominated the spectrum and became essentially independent of the incident frequency. The numerical and exploratory nature of this thesis leaves many questions unanswered and opens the way for more in depth investigations both at the theoretical and computational level.}},
author = {{Kärrholm, Gustav}},
language = {{eng}},
note = {{Student Paper}},
title = {{Photons in a twisted lattice}},
year = {{2024}},
}