Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

TT 16: Korrelierte Elektronen: Quantenstörstellen, Kondo-Physik

TT 16.5: Talk

Tuesday, March 9, 2004, 17:45–18:00, H19

Dynamics of a 3-level quantum impurity with orbital degeneracy in a fermionic bath — •Michael Arnold¹, Johann Kroha¹, and Alfred Zawadowski² — ¹Physikalisches Institut, Universität Bonn — ²Department of Physics, TU Budapest

We consider a model of an atom moving in a mexican hat-like potential with 3-fold rotational symmetry, corresponding to a small atom localized in the interstitial space of, e.g., an fcc lattice. The atom is coupled to the conduction electron sea via angular momentum scattering. The local impurity spectrum consists of the ground state and two Kramers degenerate excited states. We investigate the possibility of 2-channel Kondo correlations developing in the Kramers doublet in an intermediate energy region, in competition to the relaxation to the ground state. The two channels of the system are represented by the conduction electron spin conserved by the electron-impurity coupling. A perturbative RG scheme is used to investigate the intermediate energy region of the model. We show that, in analogy to previous work on Kondo impurities out of equilibrium [1], the running coupling constants acquire a parametric dependence on the energy of the scattering electrons, induced by the thermal excitations of the impurity system.

[1] A. Rosch, J. Paaske, J. Kroha, and P Wölfle, Phys. Rev. Lett. 90, 076804 (2003).