11,417 research outputs found
Equilibrium and off-equilibrium simulations of chiral-glass order in three-dimensional Heisenberg spin glasses
Spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin
glasses are studied both by equilibrium and off-equilibrium Monte Carlo
simulations. Fully isotropic model is found to exhibit a finite-temperature
chiral-glass transition without the conventional spin-glass order. Although
chirality is an Ising-like quantity from symmetry, universality class of the
chiral-glass transition appears to be different from that of the standard Ising
spin glass. In the off-equilibrium simulation, while the spin autocorrelation
exhibits only an interrupted aging, the chirality autocorrelation persists to
exhibit a pronounced aging effect reminisecnt of the one observed in the
mean-field model. Effects of random magnetic anisotropy is also studied by the
off-equilibrium simulation, in which asymptotic mixing of the spin and the
chirality is observed.Comment: 15 pages including 8 figures, plain Tex, to appear in Computer
Simulation Studies in Condensed Matter Physics XI, Springer, 199
Ordering of the three-dimensional Heisenberg spin glass in magnetic fields
Spin and chirality orderings of the three-dimensional Heisenberg spin glass
are studied under magnetic fields in light of the recently developed
spin-chirality decoupling-recoupling scenario. It is found by Monte Carlo
simulations that the chiral-glass transition and the chiral-glass ordered
state, which are essentially of the same character as their zero-field
counterparts, occur under magnetic fields. Implication to experimental phase
diagram is discussed.Comment: 5 pages, 3 figure
Dynamical simulation of spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin glasses
Spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin
glasses are studied with and without randaom magnetic anisotropy by dynamical
Monte Carlo simulations. In isotropic case, clear evidence of a
finite-temperature chiral-glass transition is presented. While the spin
autocorrelation exhibits only an interrupted aging, the chirality
autocorrelation persists to exhibit a pronounced aging effect reminisecnt of
the one observed in the mean-field model. In anisotropic case, asymptotic
mixing of the spin and the chirality is observed in the off-equilibrium
dynamics.Comment: 4 pages including 5 figures, LaTex, to appear in Phys. Rev. Let
Phase transition of the three-dimensional chiral Ginzburg-Landau model -- search for the chiral phase
Nature of the phase transition of regularly frustrated vector spin systems in
three dimensions is investigated based on a Ginzburg-Landau-type effective
Hamiltonian. On the basis of the variational analysis of this model, Onoda et
al recently suggested the possible occurrence of a chiral phase, where the
vector chirality exhibits a long-range order without the long-range order of
the spin [Phys. Rev. Lett. 99, 027206 (2007)]. In the present paper, we
elaborate their analysis by considering the possibility of a first-order
transition which was not taken into account in their analysis. We find that the
first-order transition indeed occurs within the variational approximation,
which significantly reduces the stability range of the chiral phase, while the
chiral phase still persists in a restricted parameter range. Then, we perform
an extensive Monte Carlo simulation focusing on such a parameter range.
Contrary to the variational result, however, we do not find any evidence of the
chiral phase. The range of the chiral phase, if any, is estimated to be less
than 0.1% in the temperature width.Comment: 19 pages, 17 figure
Ordering of the Heisenberg Spin Glass in High Dimensions
Ordering of the Heisenberg spin glass with the nearest-neighbor Gaussian
coupling is investigated by equilibrium Monte Carlo simulations in four and
five dimensions. Ordering of the mean-field Heisenberg spin-glass is also
studied for comparison. Particular attention is paid to the nature of the
spin-glass and the chiral-glass orderings. Our numerical data suggest that, in
five dimensions, the model exhibits a single spin-glass transition at a finite
temperature, where the spin-glass order accompanying the simultaneous
chiral-glass order sets in. In four dimensions, by contrast, the model exhibits
a chiral-glass transition at a finite temperature, not accompanying the
standard spin-glass order. The critical region associated with the chiral-glass
transition, however, is very narrow, suggesting that dimension four is close to
the marginal dimensionality.Comment: 18 pages, 12 figure
Ordering of the Heisenberg spin glass in two dimensions
The spin and the chirality orderings of the Heisenberg spin glass in two
dimensions with the nearest-neighbor Gaussian coupling are investigated by
equilibrium Monte Carlo simulations. Particular attention is paid to the
behavior of the spin and the chirality correlation lengths. In order to observe
the true asymptotic behavior, fairly large system size L\gsim 20 (L the linear
dimension of the system) appears to be necessary. It is found that both the
spin and the chirality order only at zero temperature. At high temperatures,
the chiral correlation length stays shorter than spin correlation length,
whereas at lower temperatures below the crossover temperature T_\times, the
chiral correlation length exceeds the spin correlation length. The spin and the
chirality correlation-length exponents are estimated above T_\times to be
\nu_SG=0.9+-0.2 and \nu_CG=2.1+-0.3, respectively. These values are close to
the previous estimates on the basis of the domain-wall-energy calculation.
Discussion is given about the asymptotic critical behavior realized below
T_\times.Comment: to appear in a special issue of J. Phys.
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