Regensburg 2004 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Tiefe Temperaturen
TT 16: Korrelierte Elektronen: Quantenstörstellen, Kondo-Physik
TT 16.7: Vortrag
Dienstag, 9. März 2004, 18:15–18:30, H19
NRG study of the Kondo effect in the presence of itinerant-electron ferromagnetism — •M. Sindel1, J. Martinek2, L. Borda1, J. Barnas3, J. König2, G. Schön2, and J. von Delft1 — 1LMU Muenchen — 2U Karlsruhe — 3U Poznan, Polen
The successful observation of the Kondo effect in molecular quantum dots (QDs) like carbon nanotubes and single molecules attached to metallic electrodes opened the possibility to study the influence of many-body correlations in the leads (superconductivity or ferromagnetism) on the Kondo effect. The Kondo effect in QDs - artificial magnetic impurities - attached to ferromagnetic leads is studied with the numerical renormalization group (NRG) method. Here we adapt this method to the case of a QD coupled to ferromagnetic leads with parallel magnetization directions. It is shown that the QD level is spin-split due to presence of ferromagnetic electrodes, leading to a suppression of the Kondo effect. The resulting splitting of the Kondo resonance is similar to the usual magnetic-field-induced splitting. We find that this splitting can be fully compensated by an appropriately tuned external magnetic field and thus the Kondo effect can be restored, confirming a recent prediction. Although the resulting Kondo resonance then has an unusual spin asymmetry with a reduced Kondo temperature, the ground state is still a locally-screened state, describable by Fermi liquid theory and a generalized Friedel sum rule, and transport in the unitary limit is not spin dependent.