Hamburg 2001 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 16: Postersitzung II: Amorphe und Tunnelsysteme, Mesoskopische Systeme, Schwere Fermionen, Kernmagnetismus

TT 16.29: Poster

Dienstag, 27. März 2001, 14:30–17:00, Rang S\ 3

Quantum effects in the quasiparticle structure of the (ferromagnetic) Kondo lattice model — •D. Meyer, C. Santos, and W. Nolting — Lehrstuhl Festkörpertheorie, Institut für Physik, Humboldt-Universität zu Berlin

We investigate the Kondo lattice model with positive and negative exchange constants J. A new “dynamical mean-field theory” based approach for the model with quantum spins is introduced. The inspection of exactly solvable limiting cases and several known approximation methods, namely the second-order perturbation theory, the self-consistent CPA and finally a moment-conserving decoupling of the equations of motion help in evaluating the new approach. This comprehensive investigation gives some certainty to our results: The J<0 and >0 cases are physically rather different. In the J>0 case, the energetically lowest states are not completely spin-polarized. A band splitting, which occurs already for relatively low interaction strengths, can be related to distinct elementary excitations, namely magnon emission (absorption) and the formation of magnetic polarons. We demonstrate the properties of the Kondo lattice model in terms of spectral densities and quasiparticle densities of states.