100 research outputs found
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
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
Exact Solution of a Vertex Model with Unlimited Number of States Per Bond
The exact solution is obtained for the eigenvalues and eigenvectors of the
row-to-row transfer matrix of a two-dimensional vertex model with unlimited
number of states per bond. This model is a classical counterpart of a quantum
spin chain with an unlimited value of spin. This quantum chain is studied using
general predictions of conformal field theory. The long-distance behaviour of
some ground-state correlation functions is derived from a finite-size analysis
of the gapless excitations.Comment: 11pages, 6 figure
Phase separation in fermionic systems with particle-hole asymmetry
We determine the ground-state phase-diagram of a Hubbard Hamiltonian with
correlated hopping, which is asymmetric under particle-hole transform. By
lowering the repulsive Coulomb interaction U at appropriate filling and
interaction parameters, the ground state separates into a hole and an electron
conducting phases: two different wave vectors characterize the system and
charge-charge correlations become incommensurate. By further decreasing U
another transition occurs at which the hole conducting region becomes
insulating, and conventional phase separation takes place. Finally, for
negative U the whole system eventually becomes a paired insulator. It is
speculated that such behavior could be at the origin of the incommensurate
superconducting phase recently discovered in the 1D Hirsch model. The exact
phase boundaries are calculated in one dimension.Comment: 4 pages, 2 figure
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
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
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 and
(), 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
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