Coulomb impurities in graphene quantum dots in a magnetic field
tarafından
 
Eren, İsmail, author.

Başlık
Coulomb impurities in graphene quantum dots in a magnetic field

Yazar
Eren, İsmail, author.

Yazar Ek Girişi
Eren, İsmail, author.

Fiziksel Tanımlama
ix, 46 leaves: charts;+ 1 computer laser optical disc.

Özet
In this thesis, we investigate the atomic collapse of Graphene Quantum Dots (GQDs) in a magnetic field with the tight-binding (TB) model and mean-field Hubbard (MFH) approximation. We placed a charged impurity at the center of GQDs, and we systematically investigated the atomic collapse effect in the magnetic field by adjusting the charge of the impurity, size of the quantum dots, and magnitude of the magnetic field. It is shown that the electronic state with the lowest energy of Graphene resembled the same effect of the lowest bound state (TLBS) of atomic collapse. We confirmed the earlier findings, and we showed that the required critical charges of TLBS of the GQDs to collapse below the Fermi level are almost equal. Additionally, we investigate the formation of resonance states of GQDs, and among these resonance states, we study the evolution of the first-formed resonance state (R1). Applying a perpendicular magnetic field to GQD, decreased the critical charge of each structure, and we found that the decrease is dependent on the dot size. Moreover, we also found that TLBS of GQDs of varying sizes are crossed each other at a particular impurity charge and energy. We used the relation between the magnetic field and magnetic length (lB), and we compared B with the radius of the GQD (RGQD) in varying sizes. We found that TLBS of a GQD still converges to a particular crossing point (in terms of impurity charge and energy) as in no magnetic field when lB > RGQD. However, TLBS of a GQD diverges from the crossing point when lB < RGQD. It is studied that the continuum form of the R1 state became a chain of separated Landau levels in a magnetic field. Here we show that Landau level formation is more noticeable, and the inter-level separation of the Landau levels becomes more prominent when the lB < RGQD. Lastly, we investigated the atomic collapse of the Hofstadter's butterflies in GQDs. We found that increasing the impurity charge collapsed the energy levels. Also, increasing the impurity charge decreased (increased) the local density of states of the impurity center at the top (bottom) part of the spectrum of the Hofstadter's butterflies.

Konu Başlığı
Magnetic fields.
 
Quantum dots.
 
Graphene.

Yazar Ek Girişi
Güçlü, Alev Devrim,

Tüzel Kişi Ek Girişi
İzmir Institute of Technology. Physics.

Tek Biçim Eser Adı
Thesis (Master)--İzmir Institute of Technology:Physics.
 
İzmir Institute of Technology: Physics --Thesis (Master).

Elektronik Erişim
Access to Electronic Versiyon.


LibraryMateryal TürüDemirbaş NumarasıYer NumarasıDurumu/İade Tarihi
IYTE LibraryTezT002347QC754.2.M3 E67 2021Tez Koleksiyonu