191,801 research outputs found
Hole correlation and antiferromagnetic order in the t-J model
We study the t-J model with four holes on a 32-site square lattice using
exact diagonalization. This system corresponds to doping level x=1/8. At the
``realistic'' parameter J/t=0.3, holes in the ground state of this system are
unbound. They have short range repulsion due to lowering of kinetic energy.
There is no antiferromagnetic spin order and the electron momentum distribution
function resembles hole pockets. Furthermore, we show evidence that in case
antiferromagnetic order exists, holes form d-wave bound pairs and there is
mutual repulsion among hole pairs. This presumably will occur at low doping
level. This scenario is compatible with a checkerboard-type charge density
state proposed to explain the ``1/8 anomaly'' in the LSCO family, except that
it is the ground state only when the system possesses strong antiferromagnetic
order
U(1) Gauge Theory of the Hubbard Model : Spin Liquid States and Possible Application to k-(BEDT-TTF)_2 Cu_2 (CN)_3
We formulate a U(1) gauge theory of the Hubbard model in the slave-rotor
representation. From this formalism it is argued that spin liquid phases may
exist near the Mott transition in the Hubbard model on triangular and honeycomb
lattices at half filling. The organic compound k-(BEDT-TTF)_2 Cu_2 (CN)_3 is a
good candidate for the spin liquid state on a triangular lattice. We predict a
highly unusual temperature dependence for the thermal conductivity of this
material.Comment: 5 pages, 2 figures; paper shortened and the phase diagram of
anisotropic triangular lattice correcte
Storage by trapping and spatial staggering of multiple interacting solitons in -type media
In this paper we investigate the properties of self induced transparency
(SIT) solitons, propagating in a -type medium. It was found that the
interaction between SIT solitons can lead to trapping with their phase
preserved in the ground state coherence of the medium. These phases can be
altered in a systematic way by the application of appropriate light fields,
such as additional SIT solitons. Furthermore, multiple independent SIT solitons
can be made to propagate as bi-solitons through their mutual interaction with a
separate light field. Finally, we demonstrate that control of the SIT soliton
phase can be used to implement an optical exclusive-or gate.Comment: 7 pages, 7 figure
Disproportionation Transition at Critical Interaction Strength: NaCoO
Charge disproportionation (CD) and spin differentiation in NaCoO
are studied using the correlated band theory approach. The simultaneous CD and
gap opening seen previously is followed through a first order charge
disproportionation transition 2Co Co+Co, whose ionic
identities are connected more closely to spin (S=0, S=1/2 respectively) than to
real charge. Disproportionation in the Co orbital is compensated by
opposing charge rearrangement in other 3d orbitals. At the transition large and
opposing discontinuities in the (all-electron) kinetic and potential energies
are slightly more than balanced by a gain in correlation energy. The CD state
is compared to characteristics of the observed charge-ordered insulating phase
in NaCoO, suggesting the Coulomb repulsion value is
concentration-dependent, with 3.5 eV.Comment: 4 pages and 4 embedded figure
Unitary Irreducible Representations of a Lie Algebra for Matrix Chain Models
There is a decomposition of a Lie algebra for open matrix chains akin to the
triangular decomposition. We use this decomposition to construct unitary
irreducible representations. All multiple meson states can be retrieved this
way. Moreover, they are the only states with a finite number of non-zero
quantum numbers with respect to a certain set of maximally commuting linearly
independent quantum observables. Any other state is a tensor product of a
multiple meson state and a state coming from a representation of a quotient
algebra that extends and generalizes the Virasoro algebra. We expect the
representation theory of this quotient algebra to describe physical systems at
the thermodynamic limit.Comment: 46 pages, no figure; LaTeX2e, amssymb, latexsym; typos correcte
On Inhomogeneity of a String Bit Model for Quantum Gravity
We study quantum gravitational effect on a two-dimensional open universe with
one particle by means of a string bit model. We find that matter is necessarily
homogeneously distributed if the influence of the particle on the size of the
universe is optimized.Comment: 16 pages, LaTeX2
Critical behavior of the three- and ten-state short-range Potts glass: A Monte Carlo study
We study the critical behavior of the short-range p-state Potts spin glass in
three and four dimensions using Monte Carlo simulations. In three dimensions,
for p = 3, a finite-size scaling analysis of the correlation length shows clear
evidence of a transition to a spin-glass phase at T_c = 0.273(5) for a Gaussian
distribution of interactions and T_c = 0.377(5) for a bimodal distribution.
These results indicate that the lower critical dimension of the 3-state Potts
glass is below three. By contrast, the correlation length of the ten-state (p =
10) Potts glass in three dimensions remains small even at very low temperatures
and thus shows no sign of a transition. In four dimensions we find that the p =
3 Potts glass with Gaussian interactions has a spin-glass transition at T_c
=0.536(3).Comment: 11 pages, 13 figures, 6 table
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