Regensburg 2002 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Tiefe Temperaturen

TT 15: Metall-Isolator-Überg
änge, Phasenüberg
änge in Quantensystemen I

TT 15.5: Vortrag

Mittwoch, 13. März 2002, 15:45–16:00, H20

Ferromagnetism in the Disordered Hubbard Model — •Krzysztof Byczuk, Martin Ulmke, and Dieter Vollhardt — Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute for Physics, University of Augsburg, D-86135 Augsburg, Germany

We investigate the ferromagnetic phase transition in an itinerant electronic system described by the Hubbard model with local disorder on the fcc lattice in the infinite dimensional limit. Solving the dynamical mean-field equations, using quantum monte-carlo method, we determine the dependence of the Curie temperature on the density of electrons, the local Hubbard interaction between the particles, and the strength of the disorder modeled by the binary-alloy distribution. We find that in the low-density system, the Curie temperature is rather weakly affected by the disorder. At higher densities, the critical temperature is strongly suppressed upon increase of the disorder. If the density of electrons is the same as the concentration of the atoms with lower atomic energy in the binary-alloy system, the Curie temperature is reduced even most strongly due to the splitting of the band and the corresponding metal-to-insulator crossover.