29 research outputs found
Nonlinear sigma model of a spin ladder containing a static single hole
In this letter we extend the nonlinear sigma model describing pure spin
ladders with an arbitrary number of legs to the case of ladders containing a
single static hole. A simple immediate application of this approach to
classical ladders is worked out.Comment: 17 pages, 2 figure
Field-induced XY behavior in the S=1/2 antiferromagnet on the square lattice
Making use of the quantum Monte Carlo method based on the worm algorithm, we
study the thermodynamic behavior of the S=1/2 isotropic Heisenberg
antiferromagnet on the square lattice in a uniform magnetic field varying from
very small values up to the saturation value. The field is found to induce a
Berezinskii-Kosterlitz-Thouless transition at a finite temperature, above which
a genuine XY behavior in an extended temperature range is observed. The phase
diagram of the system is drawn, and the thermodynamic behavior of the specific
heat and of the uniform and staggered magnetization is discussed in sight of an
experimental investigation of the field-induced XY behavior.Comment: 4 pages, 4 figure
Geometrical pinning of magnetic vortices induced by a deficit angle on a surface: anisotropic spins on a conic space background
We study magnetic vortex-like excitations lying on a conic space background.
Two types of them are obtained. Their energies appear to be linearly dependent
on the conical aperture parameter, besides of being logarithmically divergent
with the sample size. In addition, we realize a geometrical-like pinning of the
vortex, say, it is energetically favorable for it to nucleate around the
conical apex. We also study the problem of two vortices on the cone and obtain
an interesting effect on such a geometry: excitations of the same charge, then
repealing each other, may nucleate around the apex for suitable cone apertures.
We also pay attention to the problem of the vortex pair and how its
dissociation temperature depends upon conical geometry.Comment: 13 pages, 06 figures, Latex. Version accepted for PHYSICS LETTERS
Solitons in the spin-Peierls compound CuGeO 3
PACS. 75.10.Jm Quantized spin models – 75.50.Ee Antiferromagnetics,
Ground state properties of the ferrimagnetic one and two-dimensional Heisenberg model: Influence of dimerization and competitive interactions
We use the Schwinger boson mean field theory to study the effect of frustration and dimerization in the quantum ferrimagnetic model in one and two-dimensions. We calculate the spin reduction, the gap of the antiferromagnetic branch, and the spin fluctuation at T = 0 K. At finite temperature, the long-range order is destroyed because of the disappearance of the Bose condensation. The free energy, the magnetic susceptibility and the spin correlations at T = 0 K, are calculated. The effects of frustration and dimerization are discussed
The two dimensional classical anisotropic Heisenberg ferromagnetic model with nearest- and next-nearest neighbor interactions
PACS. 75.10.Hk Classical spin models – 75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.),