Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 111: Correlated Electrons: Quantum Impurities, Kondo Physics

TT 111.9: Vortrag

Freitag, 20. März 2015, 11:45–12:00, H 3005

Kondo physics of multi-orbital Anderson models studied by distributional exact diagonalization — Sareh Motahari and •David Jacob — Max Planck Institute of Microstructure Physics

The Anderson impurity model (AIM) plays a central role in the understanding of one of the most intriguing many-body phenomena, the Kondo effect, and is at the heart of Dynamical Mean-Field Theory. But solving the AIM especially in the multi-orbital case still poses a challenge, although numerically exact solvers such as continuous time quantum Monte Carlo (CTQMC) method and the numerical renormalization group (NRG) exist. However, CTQMC produces data only on the Matsubara axis, so that numerical analytic continuation to the real axis is necessary in order to calculate dynamical quantities on the real axis which is problematic. On the other hand the NRG method is computationally too demanding to be applied to realistic systems with more than one or two impurity levels. Here, we use the novel distributional exact diagonalization (DED) [1] method in order to study Kondo physics in multi-orbital Anderson models. In DED we stochastically generate a distribution of finite Anderson models that are solved by exact diagonalization, and the self-energy is obtained from the sample average. First, we demonstrate the validity of the method by calculating the dynamical properties of the single-orbital AIM and comparing with available exact results. Then we explore different situations in multi-orbital Anderson models, in particular the underscreened, overscreened and fully screened Kondo effects.

[1] M. Granth and H. U. R. Strand, Phys. Rev. B 86, 115111 (2012).