Aspects of strong correlations in low dimensions [Elektronische Ressource] / von Florian Schütz

Aspects of strong correlationsin low dimensionsDissertationzu Erlangung des Doktorgradesder Naturwissenschaftenvorgelegt beim Fachbereich Physikder Johann Wolfgang Goethe-Universit¨atin Frankfurt am MainvonFlorian Schu¨tzaus G¨ottingenFrankfurt (2005)(D F 1)vom Fachbereich Physik derJohann Wolfgang Goethe-Universit¨atals Dissertation angenommen.Dekan: Prof. Dr. W. AßmusGutachter: Prof. Dr. P. Kopietz,Prof. Dr. M.-R. ValentiDatum derDisputation: 7. September, 2005Abstract of the thesisThe challenging intricacies of strongly correlated electronic systems necessitatethe use of a variety of complementary theoretical approaches. In this thesis, weanalyze two distinct aspects of strong correlations and develop further or adaptsuitable techniques.First, we discuss magnetization transport in insulating one-dimensional spinrings described by a Heisenberg model in an inhomogeneous magnetic field. Dueto quantum mechanical interference of magnon wave functions, persistent mag-netization currents areshown to exist insuch a geometry in analogyto persistentcharge currents in mesoscopic normal metal rings.The second, longer part is dedicated to a new aspect of the functional renor-malization group technique for fermions. By decoupling the interaction via aHubbard-Stratonovich transformation, we introduce collective bosonic variablesfrom the beginning and analyze the hierarchy of flow equations for the coupledfield theory.