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Abstract
In this thesis, ab initio quantummechanical calculations are used to study the
properties of plasmons in nanostructures that involve atomic lengthscales. The
plasmon is an electronic excitation that corresponds to oscillations in the electron
charge density in metals, often visualized as water ripples in a pond where
the water represents a sea of free electrons. Plasmons on metal surfaces and
in nanostructured materials, such as metal nanoparticles and atomically thin
twodimensional materials, have several technological applications due to their
ability to confine light on nanoscale.
For a theoretical description of plasmon in such materials, where the electrons are heavily confined in one or more directions, a quantum mechanical description of the electrons in the material is necessary. In this thesis, the ab initio methods Density functional theory (DFT) and linear response timedependent DFT are applied to calculate the properties of plasmons in nanostructures in different dimensions. In order to identify and visualize localized plasmon modes, a method for calculating plasmon eigenmodes within the ab initio framework has been developed. In the studied materials, quantum mechanical effects such as coupling to singleelectronic transitions, electron spillout from the surface, tunneling, and spatial nonlocality, are shown to alter the plasmon excitations.
The studied systems include twodimensional materials, such as thin metal films, monolayer transition metal dichalcogenides, and graphene. Here, also van der Waals heterostructures (vdWh), which are stacks of different twodimensional materials, are considered. A new multiscale approach for calculating the dielectricfunction of vdWh, which extends ab initio accuracy to the description of hundreds of atomic layers, is presented. Also, onedimensional plasmons are studied in the case of atomically thin nanowires and edgestates of MoS_{2}.
For a theoretical description of plasmon in such materials, where the electrons are heavily confined in one or more directions, a quantum mechanical description of the electrons in the material is necessary. In this thesis, the ab initio methods Density functional theory (DFT) and linear response timedependent DFT are applied to calculate the properties of plasmons in nanostructures in different dimensions. In order to identify and visualize localized plasmon modes, a method for calculating plasmon eigenmodes within the ab initio framework has been developed. In the studied materials, quantum mechanical effects such as coupling to singleelectronic transitions, electron spillout from the surface, tunneling, and spatial nonlocality, are shown to alter the plasmon excitations.
The studied systems include twodimensional materials, such as thin metal films, monolayer transition metal dichalcogenides, and graphene. Here, also van der Waals heterostructures (vdWh), which are stacks of different twodimensional materials, are considered. A new multiscale approach for calculating the dielectricfunction of vdWh, which extends ab initio accuracy to the description of hundreds of atomic layers, is presented. Also, onedimensional plasmons are studied in the case of atomically thin nanowires and edgestates of MoS_{2}.
Original language  English 

Place of Publication  Kongens Lyngby 

Publisher  Technical University of Denmark 
Number of pages  156 
Publication status  Published  2015 
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 1 Finished

Theoretical Investigation of Plasmonic Materials using Electronic Structure Methods
Winther, K. T., Thygesen, K. S., Jacobsen, K. W., Schiøtz, J., Puska, M. J. & García de Abajo, F. J.
Technical University of Denmark
01/09/2011 → 13/08/2015
Project: PhD