Regensburg 2013 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 30: Correlated Electrons: Quantum Impurities, Kondo Physics

TT 30.12: Vortrag

Dienstag, 12. März 2013, 12:30–12:45, H21

Possible non-Fermi liquid behavior in transport through Co doped Au chains — •Andreas Weichselbaum¹, Solange Di Napoli², Pablo Roura-Bas², Armando A. Aligia³, Yuriy Mokrousov⁴, and Stefan Blügel⁴ — ¹Ludwig-Maximilians-Universität, München, Germany — ²Departamento de Física de la Materia Condensada, Buenos Aires, Argentina — ³Centro Atómico Bariloche and Instituto Balseiro, Bariloche, Argentina — ⁴Institut für Festkörperforschung, Forschungszentrum Jülich, Germany

We calculate the conductance as a function of temperature G(T) through monoatomic Au chains, which contain one Co atom as a magnetic impurity and are connected to two conducting leads with a 4-fold symmetry axis. Using the information derived from ab initio calculations, we construct an effective model Hamiltonian H_eff that hybridizes a 3d⁷ quadruplet at the Co site with two 3d⁸ triplets through the hopping of 5d_xz and 5d_yz electrons of Au. The quadruplet is split by a term D S_z,Co² due to spin-orbit coupling at the Co site. Solving H_eff with the numerical renormalization group (NRG), we find at low temperatures G(T) = a−b√T together with a ground state impurity entropy of ln(2)/2, a behavior similar to the two-channel Kondo model. Stretching the chain one expects a quantum phase transition to a non-Kondo phase, with the physics of the underscreened Kondo model at the quantum critical point.