173 research outputs found
Boundary S matrices for the open Hubbard chain with boundary fields
Using the method introduced by Grisaru et al., boundary S matrices for the
physical excitations of the open Hubbard chain with boundary fields are
studied. In contrast to the open supersymmetric t-J model, the boundary S
matrix for the charge excitations depend on the boundary fields though the
boundary fields do not break the spin-SU(2) symmetry.Comment: Latex,12 page
SU(2)xSU(2) Invariant Scattering Matrix of the Hubbard Model
We consider the one-dimensional half-filled Hubbard model. We show that the
excitation spectrum is given by the scattering states of four elementary
excitations, which form the fundamental representation of .
We determine the exact two-particle Scattering matrix, which a solution of the
Yang-Baxter equation and reflects the symmetry of the model. The
results for repulsive and attractive Hubbard model are related by an
interchange of spin and charge degrees of freedom.Comment: 29 pages, jyTeX (macro included - just TeX the file) ITP-SB-93-45,
BONN-HE-93-3
Scattering Matrix and Excitation Spectrum of the Hubbard Model
We consider the one-dimensional Hubbard model at half filling. We show that
both excitation spectrum and S-matrix are determined by the SO(4) symmetry of
the model. The complete set of excitations is given by the scattering states
four elementary excitations, which form the fundamental representation of
SO(4). We evaluate the exact S-matrix, which satisfies the Yang-Baxter
relation. The results for the repulsive and attractive Hubbard model are
related by an interchange of spin and charge degrees of freedom.Comment: 8 pages, jyTeX (macro included - just TeX the file) ITP-SB-93-4
Dynamical density correlation function of 1D Mott insulators in a magnetic field
We consider the one dimensional (1D) extended Hubbard model at half filling
in the presence of a magnetic field. Using field theory techniques we calculate
the dynamical density-density correlation function in the
low-energy limit. When excitons are formed, a singularity appears in
at a particular energy and momentum transfer.Comment: 7 pages, 4 figure
GAPS IN THE HEISENBERG-ISING MODEL
We report on the closing of gaps in the ground state of the critical
Heisenberg-Ising chain at momentum . For half-filling, the gap closes at
special values of the anisotropy , integer. We explain
this behavior with the help of the Bethe Ansatz and show that the gap scales as
a power of the system size with variable exponent depending on . We use
a finite-size analysis to calculate this exponent in the critical region,
supplemented by perturbation theory at . For rational
fillings, the gap is shown to be closed for {\em all} values of and
the corresponding perturbation expansion in shows a remarkable
cancellation of various diagrams.Comment: 12 RevTeX pages + 4 figures upon reques
Asymptotics and functional form of correlators in the XX - spin chain of finite length
We verify the functional form of the asymptotics of the spin - spin equal -
time correlation function for the XX-chain, predicted by the hypothesis of
conformal invariance at large distances and by the bosonization procedure. We
point out that bosonization also predicts the functional form of the
correlators for the chains of finite length. We found the exact expression for
the spin- spin equal- time correlator on finite lattice. We find the excellent
agreement of the exact correlator with the prediction given by the leading
asymptotics result up to the very small distances. We also establish the
correspondence between the value of the constant before the asymptotics for the
XX- chain with the expression for this constant proposed by Lukyanov and
Zamolodchikov. We also evaluate the constant corresponding to the subleading
term in the asymptotics in a way which is different from the previous studies.Comment: LaTex, 12 page
Formfactors and functional form of correlators in the XX spin chain
We present the new expressions for the formfactors of local operators for the
XX - quantum spin chain as a Cauchy determinants. Using the known functional
form of the correlator at large distances we propose the new expression for the
constant for the asymptotics of the correlator as a Cauchy determinant. We
calculate the momentum distribution for the general case of the XXZ spin chain
and point out that it is completely different from the Luttinger model (the
system of fermions). For the XX chain we compare numerically the value of the
lowest formfactor and the expectation value of momentum- zero operators which
is determined by the functional form of the correlator.Comment: LaTex, 18 page
On the lowest energy excitations of one-dimensional strongly correlated electrons
It is proven that the lowest excitations of one-dimensional
half-integer spin generalized Heisenberg models and half-filled extended
Hubbard models are -periodic functions. For Hubbard models at fractional
fillings , where , and is
the number of electrons per unit cell. Moreover, if one of the ground states of
the system is magnetic in the thermodynamic limit, then for
any , so the spectrum is gapless at any wave vector. The last statement is
true for any integer or half-integer value of the spin.Comment: 6 Pages, Revtex, final versio
Unusual low-temperature thermopower in the one-dimensional Hubbard model
The low-temperature thermoelectric power of the repulsive-interaction
one-dimensional Hubbard model is calculated using an asymptotic Bethe ansatz
for holons and spinons. The competition between the entropy carried by the
holons and that carried by the backflow of the spinons gives rise to an unusual
temperature and doping dependence of the thermopower which is qualitatively
similar to that observed in the normal state of high- superconductors.Comment: 11 pages, REVTEX 3.
Completeness of the SO(4) Extended Bethe Ansatz for the One-Dimensional Hubbard Model
We show how to construct a complete set of eigenstates of the hamiltonian of
the one-dimensional Hubbard model on a lattice of even length . This is done
by using the nested Bethe Ansatz {\it and} the symmetry of the model.
We discuss in detail how the counting of independent eigenstates is carried
out.Comment: 33 pages, using latex, to appear in Nucl.Phys. B (FS
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