arXiv subjects

J. A. Verges

Publications and source records attributed to J. A. Verges.

39 records · Page 3Linked to original sources

arXiv1996

A new model of quantum chaotic billiards: Spectral Statistics and Wavefunctions in 2D

Quantum chaotic dynamics is obtained for a tight-binding model in which the energies of the atomic levels at the boundary sites are chosen at random. Results for the square lattice indicate that the energy spectrum shows a complex behavior with regions that obey the Wigner-Dyson statistics and localized and quasi-ideal states distributed according to Poisson statistics. Although the averaged spatial extension of the eigenstates in the present model scales with the size of the system as in the Gaussian Orthogonal Ensemble, the fluctuations are much larger.

chao-dyn↗

arXiv1994

The wavefunction renormalization constant for the one- and two- band Hubbard hamiltonians in two dimensions

The wavefunction renormalization in the Hubbard model is studied, by using well tested mean field tecniques. The 'orthogonality catastrophe' is shown to exist, even in 2D, for doping levels sufficiently close to half filling. The results are extended beyond mean field, by constructing delocalized wavefunctions, with the correct symmetries of the exact solutions. The physics are still well described by the assumption of the existence of the orthogonality catastrophe.

cond-mat↗

arXiv1994

Hartree Fock and RPA studies of the Hubbard model

The applicability of the Hartree-Fock and random phase approximations to models of strongly correlated electrons is discussed. The 2D Hubbard model is analyzed. An antiferromagnetic phase (at half filling) and Fermi liquid behavior (at low electron densities) are found. In addition, the system shows an unconventional regime near half filling. It is characterized by the formation of spin and charge textures. Local magnetic moments and spin waves are also present, and the quasiparticle pole at the Fermi energy vanishes. The charge excitation spectrum is gapless. The overall features resemble those of the 1D Luttinger liquid.

cond-mat↗