Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Language: search.filters.language.enSubject: search.filters.subject.Electronic structure

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  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Atomic Collapse in Graphene Quantum Dots in a Magnetic Field
    (Elsevier, 2022) Eren, İsmail; Güçlü, Alev Devrim
    We investigate finite size and external magnetic field effects on the atomic collapse due to a Coulomb impurity placed at the center of a hexagonal graphene quantum dot within tight binding and mean-field Hubbard approaches. For large quantum dots, the atomic collapse effect persists when the magnetic field is present, characterized by a series of Landau level crossings and anticrossings, in agreement with previous bulk graphene results. However, we show that a new regime arises if the size of the quantum dot is comparable to or smaller than the magnetic length: While the lowest bound states cross the Fermi level at a lower value of coupling constant β<0.5, a size independent critical coupling constant βc∗>0.5 emerges in the local density of states spectrum, which increases with the applied magnetic field. These effects are found to be persistent in the presence of electron–electron interactions within mean-field Hubbard approximation.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Defect Induced Anderson Localization and Magnetization in Graphene Quantum Dots
    (Elsevier, 2018) Altıntaş, Abdulmenaf; Güçlü, Alev Devrim
    We theoretically investigate the effects of atomic defect related short-range disorders and electron-electron interactions on Anderson type localization and the magnetic properties of hexagonal armchair graphene quantum dots using an extended mean-field Hubbard model and wave packet dynamics for the calculation of localization lengths. We observe that randomly distributed defects with concentrations between 1 and 5% of the total number of atoms leads to localization alongside magnetic puddle-like structures. Although the localization lengths are not affected by interactions, staggered magnetism and localization are found to be enhanced if the defects are distributed unevenly between the sublattices of the honeycomb lattice.