ABSTRACT
We have studied the ground state of one-dimensional Hubbard superlattice structures with different unit-cell sizes in the presence of an electric field. A self-consistent Hartree-Fock approximation calculation is done in the weak- to intermediate-interaction regime. Studying the charge gap at the Fermi level and the charge density structure factor, we get an idea of how the charge modulation on the superlattice is governed by the competition between the electronic correlation and the external electric field.
ABSTRACT
We have studied finite-sized single band models with short-range pairing interactions between electrons in the presence of diagonal Fibonacci modulation in one dimension. Two models, namely the attractive Hubbard model and the Penson-Kolb model, have been investigated at half-filling at zero temperature by solving the Bogoliubov-de Gennes equations in real space within a mean-field approximation. The competition between 'disorder' and the pairing interaction leads to a suppression of superconductivity (of usual pairs with zero centre-of-mass momenta) in the strong-coupling limit while an enhancement of the pairing correlation is observed in the weak-coupling regime for both models. However, the dissimilarity of the pairing mechanisms in these two models brings about notable differences in the results. The extent to which the bond-ordered wave and the η-paired (of pairs with centre-of-mass momenta = π) phases of the Penson-Kolb model are affected by the disorder has also been studied in the present calculation. Some finite size effects are also identified.
