Suppression and revival of long-range ferromagnetic order in the multiorbital Fermi-Hubbard model

Abstract

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 eff = 1) and significantly decreases when considering three orbitals (S eff = 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 (S eff → ∞). We analyze a connection to the double-exchange model and observe high importance of spin-flip processes there as well.arXiv:1802.02935v3 [cond-mat.str-el]

Orbital ordering of ultracold alkaline-earth atoms in optical lattices

“…At ≈ 1 and variable , the Hamiltonian in Eq. ( 1) can be mapped to the double-exchange model (FM Kondo-lattice model) with both FM and AFM terms [37]. We note that away from the polarizability ratio = 1, FM ordering becomes stabilized with increasing due to the larger exchange interaction ex and the stronger localization of atoms.…”

Ce 4f electronic spectrum function in Ce3Al intermetallic compound studied via a many‐body method

“…6 The occupancy analysis indicates that Ce ions almost (about 89.2%) consist of 4f 1 configuration, together with a few contributions from the 4f 0 and 4f 2 configurations. 1 This physical picture suggests the Kondo impurity/lattice effect (below Kondo temperature), that is, f 1 valence state, 50 which also manifests itself in the local density matrix dominated by n = 1 state. In principle, the minor populations of n = 0 and n = 2 should be identified as the so-called virtual charge fluctuations in the context of Kondo model.…”