Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 18: Correlated Electrons: Quantum Impurities, Kondo Physics 2
TT 18.1: Vortrag
Dienstag, 27. März 2012, 09:30–09:45, H 3005
Dynamical Mean-Field Theory of Indirect Magnetic Exchange — •Irakli Titvinidze, Andrej Schwabe, Niklas Rother, and Michael Potthoff — I. Institut für Theoretische Physik Universität Hamburg Jungiusstraße 9 20355 Hamburg Germany
Two magnetic impurities on a metallic substrate surface experience the Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interaction. This indirect non-local magnetic exchange competes with the local Kondo effect. While the latter is described in principle exactly within single-site dynamical mean-field theory, the effects of the RKKY coupling are taken into account approximately only. Here, this is demonstrated by comparing the DMFT results with numerically exact data obtained by the density-matrix renormalization group for a one-dimensional model with two Anderson impurities. With the two-site DMFT, we also benchmark a simplified DMFT variant. Varying the inter-impurity distance d and the local exchange coupling J ∼ − V2/U, different parameter regimes with dominating Kondo physics or with dominating RKKY interaction are studied. The reliability of DMFT for magnetic nanostructures on metallic surfaces is shown to crucially depend on the respective parameter regime as well as on geometrical and finite-size effects. The prospects of DMFT (and two-site DMFT) as a reliable approach to study nanomagnetism of more complex RKKY-interacting systems are discussed.