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TT: Fachverband Tiefe Temperaturen

TT 11: Quantum Impurities, Kondo Physics

TT 11.3: Vortrag

Dienstag, 27. März 2007, 10:00–10:15, H19

Dephasing rate due to diluted Kondo impurities — Tobias Micklitz², Alexander Altland², •Theodoulos Costi¹, and Achim Rosch² — ¹Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich — ²Institut für Theoretische Physik, Universität zu Köln, 50937 Köln

We calculate the dephasing rate, 1/τ_ϕ, of electrons due to magnetic impurities in a weakly disordered metal as measured in a weak-localization experiment. For sufficiently low impurity concentrations, n_S, the dephasing rate is a universal function, 1/τ_ϕ=(n_S/ν)f(T/T_K), of T/T_K, where T_K is the Kondo scale and ν is the density of states [1,2]. Recent measurements of the dephasing rate due Fe impurities in Ag wires with T_K=4.3K [3] are shown to be well described by the above universal function for the fully screened Kondo model calculated with the numerical renormalization group method. Purely underscreened or overscreened Kondo impurities are ruled out for explaining the experiments, although a small fraction of underscreened Kondo impurities (sitting at lower symmetry sites, for example) might account for the observed slower than predicted decay of the dephasing rate at the lowest temperatures measured, T<0.1T_K.

[1] T. Micklitz et al., Phys. Rev. Lett. 96, 226601 (2006).

[2] T. Micklitz et al., cond-mat/0610304 (2006).

[3] F. Mallet et al., Phys. Rev. Lett. 97, 226804 (2006).