Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 72: Low-Dimensional Systems: Poster Session

TT 72.17: Poster

Mittwoch, 18. März 2015, 15:00–18:00, Poster B

Ferromagnetic domains due to a double exchange mechanism — •Matthias Peschke and Michael Potthoff — I. Institut für Theoretische Physik, Hamburg, Deutschland

The doped one-dimensional Kondo lattice is known to be ferromagnetic for sufficiently strong exchange coupling J. Ferromagnetism is caused by a double-exchange mechanism, i.e., electrons gain kinetic energy for ferromagnetically aligned local moments. For one-dimensional ring structures, however, this seemingly clear situation becomes much more complicated. Employing Krylov-space methods for finite Kondo lattices at strong J, we find that a singlet ground state is favored in some cases depending on the electron number and the boundary conditions. We argue that, locally, the double exchange leads to ferromagnetic alignment but globally the local moments may form a domain structure to prevent ring processes of the electrons, which are unfavorable due to the Fermi statistics or due to the boundary conditions.