Regensburg 2010 – scientific programme

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MA: Fachverband Magnetismus

MA 33: Poster II

MA 33.1: Poster

Friday, March 26, 2010, 11:00–14:00, Poster B1

Exact-exchange spin density functional study of quantum rings: Successive spin Wigner transitions and spin magnetization of the ground state. — •Thorsten Arnold, Marc Siegmund, and Oleg Pankratov — Lehrstuhl für Theoretische Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7/B2, 91058 Erlangen, Germany

We employ exact-exchange spin density functional theory to study correlated electrons on one-dimensional (1D) and two-dimensional (i.e. with finite width) quantum rings. The rings are threaded by a magnetic flux confined to the ring center, which induces a persistent current. A weak impurity potential is introduced to break the rotational symmetry. The strength of electron-electron interaction relative to kinetic energy described by parameter r_s is varied. The Fermi liquid state and the Wigner crystal state can be distinguished by resorting to the spin-resolved densities, currents and electron localization functions. Fixing the spin magnetization to admissible non-vanishing values, we found the amplitude of the spin density wave, the magnitude of the persistent current drop and the degree of electron localization to be different for spin-up and spin-down electrons. The transition point of Wigner crystallization is found at r_s<1. It crucially depends on the (effective) width of the ring. Relaxing the constraint of the spin magnetization, (for the case of the 1D ring), three ground state regimes are identified: an unpolarized Fermi liquid, an antiferromagnetic Wigner crystal and a fully polarized Fermi liquid. The transitions between these states occur in the range of rather small r_s values (r_s<1).