231 research outputs found
Vortex glass transition in a frustrated 3D XY model with disorder
The anisotropic frustrated three dimensional (3D) XY model with disorder in
the coupling constants is simulated as a model of a point disordered
superconductor in an applied magnetic field. From a finite size scaling
analysis of the helicity modulus it is concluded that the data is consistent
with a finite temperature transition with isotropic scaling and the correlation
length exponent is found to be \nu=1.50+/-0.12, consistent with 3D gauge glass
universality.Comment: For additional information, see
http://www.tp.umu.se/~olsson/VortexGlass.htm
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
Temperature Chaos and Bond Chaos in the Edwards-Anderson Ising Spin Glass : Domain-Wall Free-Energy Measurements
Domain-wall free-energy , entropy , and the correlation
function, , of are measured independently in the
four-dimensional Edwards-Anderson (EA) Ising spin glass. The stiffness
exponent , the fractal dimension of domain walls and the
chaos exponent are extracted from the finite-size scaling analysis of
, and respectively well inside the
spin-glass phase. The three exponents are confirmed to satisfy the scaling
relation derived by the droplet theory within our
numerical accuracy. We also study bond chaos induced by random variation of
bonds, and find that the bond and temperature perturbations yield the universal
chaos effects described by a common scaling function and the chaos exponent.
These results strongly support the appropriateness of the droplet theory for
the description of chaos effect in the EA Ising spin glasses.Comment: 4 pages, 6 figures; The title, the abstract and the text are changed
slightl
Scaling Analysis of Domain-Wall Free-Energy in the Edwards-Anderson Ising Spin Glass in a Magnetic Field
The stability of the spin-glass phase against a magnetic field is studied in
the three and four dimensional Edwards-Anderson Ising spin glasses. Effective
couplings and effective fields associated with length scale L are measured by a
numerical domain-wall renormalization group method. The results obtained by
scaling analysis of the data strongly indicate the existence of a crossover
length beyond which the spin-glass order is destroyed by field H. The crossover
length well obeys a power law of H which diverges as H goes to zero but remains
finite for any non-zero H, implying that the spin-glass phase is absent even in
an infinitesimal field. These results are well consistent with the droplet
theory for short-range spin glasses.Comment: 4 pages, 5 figures; The text is slightly changed, the figures 3, 4
and 5 are changed, and a few references are adde
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
Amorphous Vortex Glass Phase in Strongly Disordered Superconductors
We introduce a model describing vortices in strongly disordered
three-dimensional superconductors. The model focuses on the topological
defects, i.e., dislocation lines, in an elastic description of the vortex
lattice. The model is studied using Monte Carlo simulations, revealing a glass
phase at low temperatures, separated by a continuous phase transition to the
high temperature resistive vortex liquid phase. The critical exponents nu ~ 1.3
and eta ~ -0.4 characterizing the transition are obtained from finite size
scaling.Comment: 4 pages, 4 figure
Replica symmetry breaking transition of the weakly anisotropic Heisenberg spin glass in magnetic fields
The spin and the chirality orderings of the three-dimensional Heisenberg spin
glass with the weak random anisotropy are studied under applied magnetic fields
by equilibrium Monte Carlo simulations. A replica symmetry breaking transition
occurs in the chiral sector accompanied by the simultaneous spin-glass order.
The ordering behavior differs significantly from that of the Ising SG, despite
the similarity in the global symmetry. Our observation is consistent with the
spin-chirality decoupling-recoupling scenario of a spin-glass transition.Comment: 4 pages, 4 figure
- …