Physics / Fizik

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

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Publisher: search.filters.publisher.ElsevierSubject: search.filters.subject.Magnetization

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  • Article
    Citation - WoS: 12
    Citation - Scopus: 13
    Electronic and Magnetic Properties of Graphene Quantum Dots With Two Charged Vacancies
    (Elsevier, 2020) Kul, Erdoğan Bulut; Polat, Mustafa; Güçlü, Alev Devrim
    Electronic and magnetic properties of a system of two charged vacancies in hexagonal shaped graphene quantum dots are investigated using a mean-field Hubbard model as a function of the Coulomb potential strength ? of the charge impurities and the distance R between them. For ?=0, the magnetic properties of the vacancies are dictated by Lieb's rules where the opposite (same) sublattice vacancies are coupled antiferromagnetically (ferromagnetically) and exhibit Fermi oscillations. Here, we demonstrate the emergence of a non-magnetic regime within the subcritical region: as the Coulomb potential strength is increased to ??0.1, before reaching the frustrated atomic collapse regime, the magnetization is strongly suppressed and the ground state total spin projection is given by Sz=0 both for opposite and same sublattice vacancy configurations. When long-range electron–electron interactions are included within extended mean-field Hubbard model, the critical value for the frustrated collapse increases from ?cf?0.28 to ?cf?0.36 for R<27Å. © 2020 Elsevier Ltd
  • 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.