A new integrable two parameter model of strongly correlated electrons in one dimension

A new one-dimensional fermion model depending on two independent interaction parameters is formulated and solved exactly by the Bethe ansatz method. The Hamiltonian of the model contains the Hubbard interaction and correlated hopping as well as pair hopping terms. The density-density and pair correlations are calculated which manifest superconducting properties in certain regimes of the phase diagram.Comment: 8 pages, latex, 2 postscript figure

Integrable model of interacting XX and Fateev-Zamolodchikov chains

We consider the exact solution of a model of correlated particles, which is presented as a system of interacting XX and Fateev-Zamolodchikov chains. This model can also be considered as a generalization of the multiband anisotropic $t-J$ model in the case we restrict the site occupations to at most two electrons. The exact solution is obtained for the eigenvalues and eigenvectors using the Bethe-ansatz method.Comment: 10 pages, no figure

Interpolation between Hubbard and supersymmetric t-J models. Two-parameter integrable models of correlated electrons

Two new one-dimensional fermionic models depending on two independent parameters are formulated and solved exactly by the Bethe-ansatz method. These models connect continuously the integrable Hubbard and supersymmetric t-J models.Comment: 11pages and no figure

Pair correlation functions in one-dimensional correlated-hopping models

We investigate ground-state properties of two correlated-hopping electron models, the Hirsch and the Bariev model. Both models are of recent interest in the context of hole superconductivity. Applying the Lanczos technique to small clusters, we numerically determine the binding energy, the spin gaps, correlation functions, and other properties for various values of the bond-charge interaction parameter. Our results for small systems indicate that pairing is favoured in a certain parameter range. However, in contrast to the Bariev model, superconducting correlations are suppressed in the Hirsch model, for a bond-charge repulsion larger than a critical value.Comment: 7 pages (LaTeX) + 6 postcript figures in a separate uuencoded fil

New Integrable Models of Strongly Correlated Particles with Correlated Hopping

The exact solution is obtained for the eigenvalues and eigenvectors for two models of strongly correlated particles with single-particle correlated and uncorrelated pair hoppings. The asymptotic behavior of correlation functions are analysed in different regions, where the models exhibit different physical behavior.Comment: 12 pages, 3 figure

Exact soultion of asymmetric diffusion with second-class particles of arbitrary size

The exact solution of the asymmetric exclusion problem with particles of first and second class is presented. In this model the particles (size 1) of both classes are attached on lattice points and diffuse with equal asymmetric rates, but particles in the first class do not distinguish those in the second class from the holes (empty sites). We generalize and solve exactly this model by considering molecules in the first and second class with sizes $s_1$ and $s_2$ ($s_1,s_2 = 0,1,2,...$), in units of lattice spacing, respectively. The solution is derived by a Bethe ansatz of nested type. We give in this paper a pedagogical and simple presentation of the Bethe ansatz solution of the problem which can easily be followed by a non specialized audience in exactly integrable models.Comment: 21 pages, 7 figure

Excitation spectrum and critical exponents of a one-dimensional integrable model of fermions with correlated hopping

We investigate the excitation spectrum of a model of $N$ colour fermions with correlated hopping which can be solved by a nested Bethe ansatz. The gapless excitations of particle-hole type are calculated as well as the spin-wave like excitations which have a gap. Using general predictions of conformal field theory the long distance behaviour of some groundstate correlation functions are derived from a finite-size analysis of the gapless excitations. From the algebraic decay we show that for increasing particle density the correlation of so-called $N$-multiplets of particles dominates over the density-density correlation. This indicates the presence of bound complexes of these $N$-multiplets. This picture is also supported by the calculation of the effective mass of charge carriers.Comment: 15 pages, 3 PostScript figures appende