Time-dependent Gutzwiller theory for multiband Hubbard models.

Based on the variational Gutzwiller theory, we present a method for the computation of response functions for multiband Hubbard models with general local Coulomb interactions. The improvement over the conventional random-phase approximation is exemplified for an infinite-dimensional two-band Hubbard model where the incorporation of the local multiplet structure leads to a much larger sensitivity of ferromagnetism on the Hund coupling. Our method can be implemented into local-density approximation and Gutzwiller schemes and will therefore be an important tool for the computation of response functions for strongly correlated materials.

Antiferromagnetic order in multiband Hubbard models for iron pnictides.

We investigate multiband Hubbard models for the three iron 3d t(2g) bands and the two iron 3d e(g) bands in LaOFeAs by means of the Gutzwiller variational theory. Our analysis of the paramagnetic ground state shows that neither Hartree-Fock mean-field theories nor effective spin models describe these systems adequately. In contrast to Hartree-Fock-type approaches, the Gutzwiller theory predicts that antiferromagnetic order requires substantial values of the local Hund's-rule exchange interaction. For the three-band model, the antiferromagnetic moment fits experimental data for a broad range of interaction parameters. However, for the more appropriate five-band model, the iron e(g) electrons polarize the t(2g) electrons and they substantially contribute to the ordered moment.

Renormalization of bulk magnetic electron states at high binding energies.

The quasiparticle dynamics of electrons in a magnetically ordered state is investigated by high-resolution angle-resolved photoemission of Ni(110) at 10 K. The self-energy is extracted for high binding energies reaching up to 500 meV, using a Gutzwiller calculation as a reference frame for correlated quasiparticles. Significant deviations exist in the 300 meV range, as identified on magnetic bulk bands for the first time. The discrepancy is strikingly well described by a self-energy model assuming interactions with spin excitations. Implications relating to different electron-electron correlation regimes are discussed.

Spin-orbit coupling in ferromagnetic nickel.

We use the Gutzwiller variational theory to investigate the electronic and magnetic properties of fcc nickel. Our particular focus is on the effects of the spin-orbit coupling. Unlike standard relativistic band-structure theories, we reproduce the experimental magnetic-moment direction and we explain the change of the Fermi-surface topology that occurs when the magnetic-moment direction is rotated by an external magnetic field. The Fermi surface in our calculation deviates from early de Haas-van Alphen results. We attribute these discrepancies to an incorrect interpretation of the raw de Haas-van Alphen data.

Endotoxin and cytokines alter contractile protein expression in cardiac myocytes in vivo.

Release of bacterial endotoxin and cytokines induce cardiac failure during sepsis. We investigated the direct effects of E. coli endotoxin (lipopolysaccharide, LPS) and cytokines induced by LPS on the cardiac myocyte gene program. For in vivo-experiments adult Wistar rats were given 600 microg/day LPS i.v. for 24 h or 7 days. In addition, cultured adult rat cardiac myocytes were treated with LPS, interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNFalpha), interferon-gamma (IFNgamma) or IL-6 for 24 h. mRNA expression was evaluated for cardiac-alpha-actin (cAct), skeletal-alpha-actin (skAct), beta- and alpha-myosin heavy chain (MHC). LPS induced betaMHC-mRNA 3.6-fold and repressed alphaMHC 2.7-fold and cAct 2.5-fold after 24 h in vivo. Up-regulation of betaMHC (3-fold) and repression of cAct (2.5-fold) were still observed after 7 days LPS infusion, whereas alphaMHC-mRNA levels had returned to normal. At the protein level, increased expression of betaMHC by LPS treatment occurred already after 24 h and was maintained thereafter. LPS had no influence on skAct-mRNA. Similar changes in contractile protein mRNA expression were observed in LPS-treated cardiomyocytes in culture, whereas the tested cytokines either activated (IL-1beta, IFNgamma) or repressed (TNFalpha, IL-6) both MHC-isoforms and cAct. In conclusion, LPS and proinflammatory cytokines induce changes in contractile protein expression that may contribute to the acute heart failure observed during endotoxaemia.