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TT: Fachverband Tiefe Temperaturen

TT 17: Correlated Electrons: Spin Systems, Itinerant Magnets 2

TT 17.2: Vortrag

Montag, 11. März 2013, 15:15–15:30, H19

The phase diagram of the two-orbital Hubbard model by means of the dynamical mean field theory — •Vlastimil Křápek and Jan Kuneš — Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha, Czech Republic

The Blume-Emery-Griffiths (BEG) model with repulsive biquadratic coupling exhibits a complex multicritical phase diagram [1]. In our recent work we have shown that the two-orbital Hubbard model can be mapped on BEG model when only certain nearest-neighbor interactions are considered and that this model is relevant for the spin-state transition observed in LaCoO3 [2].

Motivated by this we explore the phase diagram of the two-orbital Hubbard model further, focusing on the following points: (1) By changing the bandwidths we can vary the metallicity of the system while keeping the parameters of the BEG model constant. (2) By changing the temperature and the crystal-field splitting we visit different phases and study the transitions between them. The two-site unit cell is used to allow for the orbital and magnetic ordering. (3) We study the effect of the number of electrons different from the half filling.
[1] W. Hoston and A. N. Berker, Phys. Rev. Lett. 67, 1027 (1991).
J. Kuneš and V. Křápek, Phys. Rev. Lett. 106, 256401 (2011).