We consider the influence of a nearest-neighbor Coulomb interaction in an extended Hubbard model and introduce an interaction term which simulates atomic polarizabilities. The inclusion of atomic polarizabilities in the model has the effect of screening the on-site Coulomb interaction for charged excitations, unlike a neighbor Coulomb interaction which reduces energies of neutral local excitations, leaving the conductivity gap unchanged. This is supported by an exact diagonalization study on small, mainly one-dimensional, extended Mott-Hubbard systems. For large V, the system undergoes a phase transition from a spin-density wave (SDW) to a charge-density wave (CDW). It is shown that the SDW/CDW phase transition cannot be described correctly when using effective parameters, but that screening effects have to be included explicitly. Also other phases, one of which is ferroelectric, appear when atomic polarizabilities are included in the model Hamiltonian. We study ${\mathrm{C}}_{60}$ in terms of the degenerate extended Hubbard model with screening effects.We consider the influence of a nearest-neighbor Coulomb interaction in an extended Hubbard model and introduce an interaction term which simulates atomic polarizabilities. The inclusion of atomic polarizabilities in the model has the effect of screening the on-site Coulomb interaction for charged excitations, unlike a neighbor Coulomb interaction which reduces energies of neutral local excitations, leaving the conductivity gap unchanged. This is supported by an exact diagonalization study on small, mainly one-dimensional, extended Mott-Hubbard systems. For large V, the system undergoes a phase transition from a spin-density wave (SDW) to a charge-density wave (CDW). It is shown that the SDW/CDW phase transition cannot be described correctly when using effective parameters, but that screening effects have to be included explicitly. Also other phases, one of which is ferroelectric, appear when atomic polarizabilities are included in the model Hamiltonian. We study ${\mathrm{C}}_{60}$ in terms of the degenerate extended Hubbard model with screening effects.

Physical review. B, Condensed matterJul 15, 199527 citations

Screening in Hubbard models with long-range interactions

Anonymous

Physical review. B./Physical review. BMay 13, 20250 citations

Bad Metallic Transport in a Modified Hubbard Model

Connie H. Mousatov, Ilya Esterlis, Sean A. Hartnoll

Strongly correlated metals often display anomalous transport, including T-linear resistivity above the Mott-Ioffe-Regel limit. We introduce a tractable microscopic model for bad metals, by restoring in the well-known Hubbard model-with hopping t and on-site repulsion U-a "screened Coulomb" interaction between charge densities that decays exponentially with spatial separation. This interaction lifts the extensive degeneracy in the spectrum of the t=0 Hubbard model, allowing us to fully characterize the small t electric, thermal, and thermoelectric transport in our strongly correlated model. Throughout the phase diagram we observe T-linear resistivity above the Mott-Ioffe-Regel limit, together with strong violation of the Wiedemann-Franz law and a large thermopower that can undergo sign change.Strongly correlated metals often display anomalous transport, including T-linear resistivity above the Mott-Ioffe-Regel limit. We introduce a tractable microscopic model for bad metals, by restoring in the well-known Hubbard model-with hopping t and on-site repulsion U-a "screened Coulomb" interaction between charge densities that decays exponentially with spatial separation. This interaction lifts the extensive degeneracy in the spectrum of the t=0 Hubbard model, allowing us to fully characterize the small t electric, thermal, and thermoelectric transport in our strongly correlated model. Throughout the phase diagram we observe T-linear resistivity above the Mott-Ioffe-Regel limit, together with strong violation of the Wiedemann-Franz law and a large thermopower that can undergo sign change.

arXiv:1803.08054Physical Review LettersMay 10, 201939 citations

Metallic state of the Hubbard model with randomly distributed Coulomb interactions

Tetsuya Mutou

We study the inhomogeneous Hubbard model with randomly distributed impurity sites with Coulomb interactions embedded in noninteracting host sites, using the dynamical mean-field theory extended to the case with site-dependent Coulomb interactions. Comparison is made with the Hubbard model which possesses the averaged effective Coulomb interactions which are proportional to impurity concentrations. For high concentrations, such a picture with the averaged effective Coulomb interactions gives reasonable results for some quantities, such as the density of states at low temperatures. At high temperatures, however, components of impurity sites and host sites are separated, leading to a clear difference from those in the homogeneous case. On the other hand, for lower concentrations, the difference appears even at low temperatures. Impurity concentration dependences of the coefficient of the specific heat linear in T and the coefficient of the resistivity square in T are different from those of the homogeneous one with the effective Coulomb interactions. In the inhomogeneous system, the high-concentration regime described by the Fermi liquid is continuously connected to the low-concentration regime which may be described by the ensemble of Kondo impurities.We study the inhomogeneous Hubbard model with randomly distributed impurity sites with Coulomb interactions embedded in noninteracting host sites, using the dynamical mean-field theory extended to the case with site-dependent Coulomb interactions. Comparison is made with the Hubbard model which possesses the averaged effective Coulomb interactions which are proportional to impurity concentrations. For high concentrations, such a picture with the averaged effective Coulomb interactions gives reasonable results for some quantities, such as the density of states at low temperatures. At high temperatures, however, components of impurity sites and host sites are separated, leading to a clear difference from those in the homogeneous case. On the other hand, for lower concentrations, the difference appears even at low temperatures. Impurity concentration dependences of the coefficient of the specific heat linear in T and the coefficient of the resistivity square in T are different from those of the homogeneous one with the effective Coulomb interactions. In the inhomogeneous system, the high-concentration regime described by the Fermi liquid is continuously connected to the low-concentration regime which may be described by the ensemble of Kondo impurities.

Physical review. B, Condensed matterJul 15, 19997 citations

{\mathrm{C}}_{60}

in terms of the degenerate extended Hubbard model with screening effects.