Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 74: Correlated Electrons: Quantum Impurities, Kondo Physics

TT 74.3: Vortrag

Mittwoch, 2. April 2014, 15:30–15:45, BEY 81

Spatial and temporal propagation of Kondo correlations — •Benedikt Lechtenberg and Frithjof B. Anders — Technische Universität Dortmund, Lehrstuhl für Theoretische Physik II, 44221 Dortmund

While the equilibrium properties of the Kondo problem are theoretically well understood, its non-equilibrium properties are subject to recent research. To set the stage, we present the spatial correlation function ⟨ S_imp^→s^→(r) ⟩ between the impurity spin S_imp^→ and the spin density of the conduction electrons in thermodynamic equilibrium using the numerical renormalization group (NRG). Then, we will address the key question, how this spatial correlation function builds up as function of time starting from an initially decoupled impurity spin. We will show that the spatial and temporal Kondo correlations propagate along a light-cone determined by the Fermi-velocity. Surprisingly, we find that ⟨ S_imp^→s^→(r) ⟩(t) contains significant non-exponential contributions outside of the light-cone. Augmenting our time-dependent NRG calculation with perturbative expansion of the density operator we can explicitly trace the origin of these correlations to the intrinsic spin-density correlations of the initial Fermi see. Contributions outside of the light-cone only vanish in a true linear response function.