18,182 research outputs found
Critical behavior of spin and chiral degrees of freedom in three-dimensional disordered XY models studied by the nonequilibrium aging method
The critical behavior of the gauge-glass and the XY spin-glass models in
three dimensions is studied by analyzing their nonequilibrium aging dynamics. A
new numerical method, which relies on the calculation of the two-time
correlation and integrated response functions, is used to determine both the
critical temperature and the nonequilibrium scaling exponents, both for spin
and chiral degrees of freedom. First, the ferromagnetic XY model is studied to
validate this nonequilibirum aging method (NAM), since for this nondisordered
system we can compare with known results obtained with standard equilibrium and
nonequilibrium techniques. When applied to the case of the gauge-glass model,
we show that the NAM allows us to obtain precise and reliable values of its
critical quantities, improving previous estimates. The XY spin-glass model with
both Gaussian and bimodal bond distributions, is analyzed in more detail. The
spin and the chiral two-time correlation and integrated response functions are
calculated in our simulations. The results obtained mainly for Gaussian and, to
a lesser extent, for bimodal interactions, support the existence of a
spin-chiral decoupling scenario, where the chiral order occurs at a finite
temperature while the spin degrees of freedom order at very low or zero
temperature.Comment: 15 pages, 15 figures. Phys. Rev. B 89, 024408 (2014
Multipolar expansion of the electrostatic interaction between charged colloids at interfaces
The general form of the electrostatic potential around an arbitrarily charged
colloid at an interface between a dielectric and a screening phase (such as air
and water, respectively) is analyzed in terms of a multipole expansion. The
leading term is isotropic in the interfacial plane and varies with
where is the in--plane distance from the colloid. The electrostatic
interaction potential between two arbitrarily charged colloids is likewise
isotropic and , corresponding to the dipole--dipole interaction
first found for point charges at water interfaces. Anisotropic interaction
terms arise only for higher powers with .Comment: 6 pages, mathematical details adde
Transport properties and structures of vortex matter in layered superconductors
In this paper we analyze the structure, phase transitions and some transport
properties of the vortex system when the external magnetic field lies parallel
to the planes in layered superconductors. We show that experimental results for
resistivity are qualitatively consistent with numerical simulations that
describe the melting of a commensurate rotated lattice. However for some
magnetic fields, the structure factor indicates the occurrence of smectic peaks
at an intermediate temperature regime.Comment: 8 pages, 8 eps figure
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