Physics / Fizik

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

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2014 - 20162

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Publisher: search.filters.publisher.John Wiley and Sons Inc.Subject: search.filters.subject.Two-dimensional materials

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  • Article
    Citation - WoS: 8
    Citation - Scopus: 9
    Sublattice Engineering and Voltage Control of Magnetism in Triangular Single and Bi-Layer Graphene Quantum Dots
    (John Wiley and Sons Inc., 2016) Güçlü, Alev Devrim; Potasz, P.; Hawrylak, Pawel
    When a Dirac electron is confined to a triangular graphene quantum dot with zigzag edges, its low-energy spectrum collapses to a shell of degenerate states at the Fermi level leading to a magnetized edge. The shell degeneracy and the total magnetization are proportional to the edge size and can be made macroscopic. In this review, we start with a general discussion of magnetic properties of graphene structures and its relation to broken sublattice symmetry. Then, we discuss single electronic properties of single and bilayer triangular graphene quantum dots, focusing on the nature of edge states. Finally, we investigate the role of electronic correlations in determining the nature of ground state and excitation spectra of triangular graphene quantum dots as a function of dot size and filling fraction of the shell of zero-energy states. The interactions are treated by a combination of tight-binding, Hartree-Fock and configuration interaction methods. We show that the spin polarization of the triangular graphene quantum dots can be controlled through gating, i.e., by adding or removing electrons. In bilayer graphene dots, the relative filling of edge states in each layer and the magnetization can be tuned down to single localized spin using an external vertical electrical field.
  • Article
    Citation - WoS: 14
    Citation - Scopus: 14
    Formation and Diffusion Characteristics of Pt Clusters on Graphene, 1h-Mos2 and 1t-Tas2
    (John Wiley and Sons Inc., 2014) Özaydın, H. Duygu; Şahin, Hasan; Şenger, Ramazan Tuğrul; Peeters, François M.
    Many experiments have revealed that the surfaces of graphene and graphene-like structures can play an active role as a host surface for clusterization of transition metal atoms. Motivated by these observations, we investigate theoretically the adsorption, diffusion and magnetic properties of Pt clusters on three different two-dimensional atomic crystals using first principles density functional theory. We found that monolayers of graphene, molybdenum disulfide (1H-MoS2) and tantalum disulfide (1T-TaS2) provide different nucleation characteristics for Pt cluster formation. At low temperatures, while the bridge site is the most favorable site where the growth of a Pt cluster starts on graphene, top-Mo and top-Ta sites are preferred on 1H-MoS2 and 1T-TaS2, respectively. Ground state structures and magnetic properties of Ptn clusters (n = 2,3,4) on three different monolayer crystal structures are obtained. We found that the formation of Pt2 dimer and a triangle-shaped Pt3 cluster perpendicular to the surface are favored over the three different surfaces. While bent rhombus shaped Pt4 is formed on graphene, the formation of tetrahedral shaped clusters are more favorable on 1H-MoS2 and 1T-TaS2. Our study of the formation of Ptn clusters on three different monolayers provides a gateway for further exploration of nanocluster formations on various surfaces.