Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 2: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles I (jointly with TT)

O 2.5: Talk

Monday, March 26, 2012, 11:45–12:00, HE 101

Multi-orbital Kondo physics of Co in Cu hosts — •Tim Wehling¹, Brigitte Surer², Matthias Troyer², Philipp Werner², Andreas Läuchli³, Aljoscha Wilhelm¹, and Alexander Lichtenstein¹ — ¹1. Institut für Theoretische Physik, Universität Hamburg, D-20355 Hamburg, Germany — ²Theoretische Physik, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland — ³Institut für Theoretische Physik, Universität Innsbruck, Technikerstrasse 25/2, A-6020 Innsbruck, Austria

We investigate the electronic structure of cobalt atoms on a copper surface and in a copper host by combining density functional calculations with a numerically exact continuous-time quantum Monte Carlo treatment of the five-orbital impurity problem. In both cases we find low energy resonances in the density of states of all five Co d-orbitals. The corresponding self-energies indicate the formation of a Fermi liquid state at low temperatures. Our calculations yield the characteristic energy scale – the Kondo temperature – for both systems in good agreement with experiments. We quantify the charge fluctuations in both geometries and suggest that Co in Cu must be described by an Anderson impurity model rather than by a model assuming frozen impurity valency at low energies. We show that fluctuations of the orbital degrees of freedom are crucial for explaining the Kondo temperatures obtained in our calculations and measured in experiments.