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    Enhanced intervalley scattering in artificially stacked double-layer graphene
    (Iop Publishing Ltd, 2014) Iqbal, M. Z.; Kelekci, Ozgur; Iqbal, M. W.; Jin, Xiaozhan; Hwang, Chanyong; Eom, Jonghwa
    We fabricated artificially stacked double-layer graphene by sequentially transferring graphene grown by chemical vapor deposition. The double-layer graphene was characterized by Raman spectroscopy and transport measurements. A weak localization effect was observed for different charge carrier densities and temperatures. The obtained intervalley scattering rate was unusually high compared to normal Bernal-stacked bilayer or single-layer graphene. The sharp point defects, local deformation, or bending of graphene plane required for intervalley scattering from one Dirac cone to another seemed to be enhanced by the artificially stacked graphene layers.
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    Öğe
    Supersymmetry and non-Abelian T-duality in type II supergravity
    (Iop Publishing Ltd, 2015) Kelekci, Ozgur; Lozano, Yolanda; Macpherson, Niall T.; Colgain, Eoin O.
    We study the effect of T-duality on supersymmetry in the context of type II supergravity. For both U(1) Abelian and SU(2) non-Abelian T-duality, we demonstrate that the supersymmetry variations after T-duality are related to the variations before T-duality through the Kosmann spinorial Lie derivative, which vanishes when the Killing spinors are independent of the T-duality directions. As a byproduct of our analysis, we present closed expressions for SU(2) T-duality in a class of spacetimes with diagonal Bianchi IX symmetry and comment on specific examples of T-dual geometries, including a novel AdS(3) geometry with large N = (4, 4) superconformal symmetry.