1,704 research outputs found
Bethe ansatz solution of the closed anisotropic supersymmetric U model with quantum supersymmetry
The nested algebraic Bethe ansatz is presented for the anisotropic
supersymmetric model maintaining quantum supersymmetry. The Bethe ansatz
equations of the model are obtained on a one-dimensional closed lattice and an
expression for the energy is given.Comment: 7 pages (revtex), minor modifications. To appear in Mod. Phys. Lett.
Thermal and magnetic properties of integrable spin-1 and spin-3/2 chains with applications to real compounds
The ground state and thermodynamic properties of spin-1 and spin-3/2 chains
are investigated via exactly solved su(3) and su(4) models with physically
motivated chemical potential terms. The analysis involves the Thermodynamic
Bethe Ansatz and the High Temperature Expansion (HTE) methods. For the spin-1
chain with large single-ion anisotropy, a gapped phase occurs which is
significantly different from the valence-bond-solid Haldane phase. The
theoretical curves for the magnetization, susceptibility and specific heat are
favourably compared with experimental data for a number of spin-1 chain
compounds. For the spin-3/2 chain a degenerate gapped phase exists starting at
zero external magnetic field. A middle magnetization plateau can be triggered
by the single-ion anisotropy term. Overall, our results lend further weight to
the applicability of integrable models to the physics of low-dimensional
quantum spin systems. They also highlight the utility of the exact HTE method.Comment: 38 pages, 15 figure
Open t-J chain with boundary impurities
We study integrable boundary conditions for the supersymmetric t-J model of
correlated electrons which arise when combining static scattering potentials
with dynamical impurities carrying an internal degree of freedom. The latter
differ from the bulk sites by allowing for double occupation of the local
orbitals. The spectrum of the resulting Hamiltonians is obtained by means of
the algebraic Bethe Ansatz.Comment: LaTeX2e, 9p
Exact solution of a spin-ladder model
An integrable spin-ladder model with nearest-neighbor exchanges and
biquadratic interactions is proposed. With the Bethe ansatz solutions of the
model hamiltonian, it is found that there are three possible phases in the
ground state, i.e., a rung-dimerized phase with a spin gap, and two massless
phases. The possible fixed points of the system and the quantum critical
behavior at the critical point are discussed.Comment: 6page Revtex, no figur
Integrability of the Heisenberg Chains with Boundary Impurities and Their Bethe Ansatz
In this paper, we show the integrability of spin-1/2 XXZ Heisenberg chain
with two arbitrary spin boundary Impurities. By using the fusion method, we
generalize it to the spin-1 XXZ chain. Then the eigenvalues of Hamiltonians of
these models are obtained by the means of Bethe ansatz method.Comment: 13 pages, latex, no figures, to be appeared in J.Phys.
Open su(4)-invariant spin ladder with boundary defects
The integrable su(4)-invariant spin-ladder model with boundary defect is
studied using the Bethe ansatz method. The exact phase diagram for the ground
state is given and the boundary quantum critical behavior is discussed. It
consists of a gapped phase in which the rungs of the ladder form singlet states
and a gapless Luttinger liquid phase. It is found that in the gapped phase the
boundary bound state corresponds to an unscreened local moment, while in the
Luttinger liquid phase the local moment is screened at low temperatures in
analogy to the Kondo effect.Comment: Revtex 9 pages, published in PR
Metal insulator transition in TlSr2CoO5 from orbital degeneracy and spin disproportionation
To describe the metal insulator transition in the new oxide TlSr2CoO5 we
investigate its electronic structure by LDA and model Hartree-Fock
calculations. Within LDA we find a homogeneous metallic and ferromagnetic
ground state, but when including the Coulomb interaction more explicitly within
the Hartree-Fock approximation, we find an insulating state of lower energy
with both spin and orbital order. We also interpret our results in terms of a
simple model.Comment: 8 pages, 9 figure
Quantum Group Invariant Supersymmetric t-J Model with periodic boundary conditions
An integrable version of the supersymmetric t-J model which is quantum group
invariant as well as periodic is introduced and analysed in detail. The model
is solved through the algebraic nested Bethe ansatz method.Comment: 11 pages, LaTe
Exact Results for a Kondo Problem in One Dimensional t-J Model
We propose an integrable Kondo problem in a one-dimensional (1D) model.
With the open boundary condition of the wave functions at the impurity sites,
the model can be exactly solved via Bethe ansatz for a class of
(Kondo coupling constants) and (impurity potentials) parametrized by
a single parameter . The integrable value of runs from negative
infinity to positive infinity, which allows us to study both the ferromagnetic
Kondo problem and antiferromagnetic Kondo problem in a strongly correlated
electron system. Generally, there is a residual entropy for the ground state,
which indicates a typical non-Fermi liquid behavior.Comment: 5 pages Revtex, no figure
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