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Regensburg 2019 – scientific programme

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MA: Fachverband Magnetismus

MA 15: Magnetism Poster A

MA 15.25: Poster

Tuesday, April 2, 2019, 10:00–13:00, Poster E

Suppression and revival of long-range ferromagnetic order in the multiorbital Fermi-Hubbard model — •Agnieszka Cichy1,2 and Andrii Sotnikov31Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland — 2Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, Staudingerweg 7, D-55099 Mainz, Germany — 3Institute of Solid State Physics, TU Wien, Wiedner Hauptstrasse 8, 1020 Vienna, Austria

By means of dynamical mean-field theory allowing for complete account of SU(2) rotational symmetry of interactions between spin-1/2 particles, we observe a strong effect of suppression of ferromagnetic order in the multiorbital Fermi-Hubbard model in comparison with a widely used restriction to density-density interactions. In the case of orbital degeneracy, we show that the suppression effect is the strongest in the two-orbital model (with effective spin S=1) and significantly decreases when considering three orbitals (S=3/2), thus magnetic ordering can effectively revive for the same range of parameters, in agreement with arguments based on vanishing of quantum fluctuations in the limit of classical spins. We analyze a connection to the double-exchange model and observe high importance of spin-flip processes there as well.

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