Materials Research and Technology

Biography

Biography: Raymond Fresard

Abstract

The cooperative properties of strongly correlated electrons have often been related to key technologies, for instance with the aim of developing high capacitance hetero-structures. In this contribution we unravel the electrical permittivity contained in the extended two-dimensional Hubbard model. Regarding static properties we consider a pair of plates hosting correlated electrons separated by a dielectric medium, that comprise a capacitor. We show that the natural tendency towards phase separation harbored in the two-dimensional Hubbard model extended by over-screened Coulomb interaction results in an increase of the capacitance. This effect competes with the electrostatic contribution and in a thermodynamically stable state we find it to be enhanced by the proximity to a van Hove singularity. The mutual influence of the interaction parameters and the distance of the van Hove singularity to half-filling are also discussed, as well as the parameters controlling the disparity of the capacitance and the compressibility. The dynamical properties will be addressed as well. It will be shown that the spectra generically consists of a continuum, a gapless collective mode with anisotropic zero-sound velocity and a correlation induced high-frequency mode dispersing at energies close to the Hubbard U. The influence of the loss of the particle-hole symmetry on these spectra will be presented too.