1,821 research outputs found
New Family of Solvable 1D Heisenberg Models
Starting from a Calogero--Sutherland model with hyperbolic interaction
confined by an external field with Morse potential we construct a Heisenberg
spin chain with exchange interaction on a lattice given
in terms of the zeroes of Laguerre polynomials. Varying the strength of the
Morse potential the Haldane--Shastry and harmonic spin chains are reproduced.
The spectrum of the models in this class is found to be that of a classical
one-dimensional Ising chain with nonuniform nearest neighbour coupling in a
nonuniform magnetic field which allows to study the thermodynamics in the limit
of infinite chains.Comment: 8 pp, LaTeX, ITP-UH-07/9
Properties of the chiral spin liquid state in generalized spin ladders
We study zero temperature properties of a system of two coupled quantum spin
chains subject to fields explicitly breaking time reversal symmetry and parity.
Suitable choice of the strength of these fields gives a model soluble by Bethe
Ansatz methods which allows to determine the complete magnetic phase diagram of
the system and the asymptotics of correlation functions from the finite size
spectrum. The chiral properties of the system for both the integrable and the
nonintegrable case are studied using numerical techniques.Comment: 19 pages, 9eps figures, Late
Theory of quasi-one dimensional imbalanced Fermi gases
We present a theory for a lattice array of weakly coupled one-dimensional
ultracold attractive Fermi gases (1D `tubes') with spin imbalance, where strong
intratube quantum fluctuations invalidate mean field theory. We first construct
an effective field theory, which treats spin-charge mixing exactly, based on
the Bethe ansatz solution of the 1D single tube problem. We show that the 1D
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state is a two-component Luttinger
liquid, and its elementary excitations are fractional states carrying both
charge and spin. We analyze the instability of the 1D FFLO state against
inter-tube tunneling by renormalization group analysis, and find that it flows
into either a polarized Fermi liquid or a FFLO superfluid, depending on the
magnitude of interaction strength and spin imbalance. We obtain the phase
diagram of the quasi-1D system and further determine the scaling of the
superfluid transition temperature with intertube coupling.Comment: new expanded version, 8 pages, updated reference
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
Dispersion relations and speeds of sound in special sectors for the integrable chain with alternating spins
Based on our previous analysis \cite{doerfel3} of the anisotropic integrable
chain consisting of spins and we compare the dispersion relations
for the sectors with infinite Fermi zones. Further we calculate the speeds of
sound for regions close to sector borders, where the Fermi radii either vanish
or diverge, and compare the results.Comment: 11 pages, LaTeX2e, uses iopart.cls,graphicx.sty and psfrag.sty, 2
figure
Exactly solvable quantum spin ladders associated with the orthogonal and symplectic Lie algebras
We extend the results of spin ladder models associated with the Lie algebras
to the case of the orthogonal and symplectic algebras $o(2^n),\
sp(2^n)$ where n is the number of legs for the system. Two classes of models
are found whose symmetry, either orthogonal or symplectic, has an explicit n
dependence. Integrability of these models is shown for an arbitrary coupling of
XX type rung interactions and applied magnetic field term.Comment: 7 pages, Late
Correlation functions of one-dimensional Bose-Fermi mixtures
We calculate the asymptotic behaviour of correlation functions as a function
of the microscopic parameters for a Bose-Fermi mixture with repulsive
interaction in one dimension. For two cases, namely polarized and unpolarized
fermions the singularities of the momentum distribution functions are
characterized as a function of the coupling constant and the relative density
of bosons.Comment: RevTeX 4, 10 pages, 2 figure
Phase diagram of an exactly solvable t-J ladder model
We study a system of one-dimensional t-J models coupled to a ladder system. A
special choice of the interaction between neighbouring rungs leads to an
integrable model with supersymmetry, which is broken by the presence of rung
interactions. We analyze the spectrum of low-lying excitations and ground state
phase diagram at zero temperature.Comment: LaTeX, 8 pp. incl. 1 figur
Determinant representation for a quantum correlation function of the lattice sine-Gordon model
We consider a completely integrable lattice regularization of the sine-Gordon
model with discrete space and continuous time. We derive a determinant
representation for a correlation function which in the continuum limit turns
into the correlation function of local fields. The determinant is then embedded
into a system of integrable integro-differential equations. The leading
asymptotic behaviour of the correlation function is described in terms of the
solution of a Riemann Hilbert Problem (RHP) related to the system of
integro-differential equations. The leading term in the asymptotical
decomposition of the solution of the RHP is obtained.Comment: 30 pages Latex2e, 2 Figures, epsf. Significantly extended and revised
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