Physical review. B, Condensed matter
Optical conductivity of the Hubbard model
J. J. Vicente Alvarez, C. A. Balseiro, Hermenegildo Alejandro Ceccatto
Abstract
We study the response to a static electric field (charge stiffness) and the frequency-dependent conductivity of the Hubbard model in a resonant-valence-bond-type paramagnetic phase. This phase is described by means of a charge and spin rotational-invariant approach, based on a mixed fermion-boson representation of the original strongly correlated electrons. We found that the Mott transition at half filling is well described by the charge stiffness behavior, and that the values for this quantity off half filling agree reasonably well with numerical results. Furthermore, for the frequency-dependent conductivity we trace back to the origin of the band that appears inside the Hubbard gap to magnetic pair breaking. This points to a magnetic origin of the midinfrared band in high-${T}_{c}$ compounds.