21 research outputs found
Magnetic Phase Diagram of the Ferromagnetically Stacked Triangular XY Antiferromagnet: A Finite-Size Scaling Study
Histogram Monte-Carlo simulation results are presented for the magnetic-field
-- temperature phase diagram of the XY model on a stacked triangular lattice
with antiferromagnetic intraplane and ferromagnetic interplane interactions.
Finite-size scaling results at the various transition boundaries are consistent
with expectations based on symmetry arguments. Although a molecular-field
treatment of the Hamiltonian fails to reproduce the correct structure for the
phase diagram, it is demonstrated that a phenomenological Landau-type
free-energy model contains all the esstential features. These results serve to
complement and extend our earlier work [Phys. Rev. B {\bf 48}, 3840 (1993)].Comment: 5 pages (RevTex 3.0), 6 figures available upon request, CRPS 93-
Histogram Monte Carlo study of multicritical behavior in the hexagonal easy-axis Heisenberg antiferromagnet
The results of a detailed histogram Monte-Carlo study of critical-fluctuation
effects on the magnetic-field temperature phase diagram associated with the
hexagonal Heisenberg antiferromagnet with weak axial anisotropy are reported.
The multiphase point where three lines of continuous transitions merge at the
spin-flop boundary exhibits a structure consistent with scaling theory but
without the usual umbilicus as found in the case of a bicritical point.Comment: 7 pages (RevTex 3.0), 1 figure available upon request, CRPS-93-1
Magnetic Phase Diagram of the Ferromagnetically Stacked Triangular Ising Antiferromagnet
Histogram Monte-Carlo simulation results are presented for the magnetic-field
-- temperature phase diagram of the Ising model on a stacked triangular lattice
with antiferromagnetic intraplane and ferromagnetic interplane interactions.
Finite-size scaling results for this frustrated system at three points along
the paramagnetic transition boundary are presented which strongly suggest a
line of triciritcal points at low field and a first-order transition line at
higher fields. These results are compared with the corresponding phase diagrams
from conventional mean-field theory as well as from the Monte Carlo mean-field
calculations of Netz and Berker [Phys. Rev. Lett. {\bf 66}, 377 (1991)].Comment: 6 pages (RevTex 3.0), 8 figures available upon reques
Magnetic-Field Induced First-Order Transition in the Frustrated XY Model on a Stacked Triangular Lattice
The results of extensive Monte Carlo simulations of magnetic-field induced
transitions in the xy model on a stacked triangular lattice with
antiferromagnetic intraplane and ferromagnetic interplane interactions are
discussed. A low-field transition from the paramagnetic to a 3-state (Potts)
phase is found to be very weakly first order with behavior suggesting
tricriticality at zero field. In addition to clarifying some long-standing
ambiguity concerning the nature of this Potts-like transition, the present work
also serves to further our understanding of the critical behavior at ,
about which there has been much controversy.Comment: 10 pages (RevTex 3.0), 4 figures available upon request, CRPS-93-0
Phenomenological model of elastic distortions near the spin-Peierls transition in
A phenomenological model of the Landau type forms the basis for a study of
elastic distortions near the spin-Peierls transition in . The
atomic displacements proposed by Hirota {\it et al.} [Phys. Rev. Lett. {\bf
73}, 736 (1994)] are accounted for by the model which includes linear coupling
between and distortions. displacements are seen to be responsible
for anomalies in the elastic properties {\it at} , whereas incipient
distortions give rise to temperature dependence below . A discussion of
possible critical behavior is also made.Comment: 1 figure available upon reques
Tricritical behavior of the frustrated XY antiferromagnet
Extensive histogram Monte-Carlo simulations of the XY antiferromagnet on a
stacked triangular lattice reveal exponent estimates which strongly favor a
scenario of mean-field tricritical behavior for the spin-order transition. The
corresponding chiral-order transition occurs at the same temperature but
appears to be decoupled from the spin-order. These results are relevant to a
wide class of frustrated systems with planar-type order and serve to resolve a
long-standing controversy regarding their criticality.Comment: J1K 2R1 4 pages (RevTex 3.0), 4 figures available upon request,
Report# CRPS-94-0
Histogram Monte Carlo study of next-nearest-neighbor Ising antiferromagnet on a stacked triangular lattice
Critical properties of the Ising model on a stacked triangular lattice, with
antiferromagnetic first and second-neighbor in-plane interactions, are studied
by extensive histogram Monte Carlo simulations. The results, in conjunction
with the recently determined phase diagram, strongly suggest that the
transition from the period-3 ordered state to the paramagnetic phase remains in
the xy universality class. This conclusion is in contrast with a previous
suggestion of mean-field tricritical behavior.Comment: 13 pages (RevTex 3.0), 10 figures available upon request, CRPS-93-0
Strong-coupling perturbation theory for the two-dimensional Bose-Hubbard model in a magnetic field
The Bose-Hubbard model in an external magnetic field is investigated with
strong-coupling perturbation theory. The lowest-order secular equation leads to
the problem of a charged particle moving on a lattice in the presence of a
magnetic field, which was first treated by Hofstadter. We present phase
diagrams for the two-dimensional square and triangular lattices, showing a
change in shape of the phase lobes away from the well-known power-law behavior
in zero magnetic field. Some qualitative agreement with experimental work on
Josephson-junction arrays is found for the insulating phase behavior at small
fields.Comment: 7 pages, 5 figures include
Ordered phase and scaling in models and the three-state antiferromagnetic Potts model in three dimensions
Based on a Renormalization-Group picture of symmetric models in three
dimensions, we derive a scaling law for the order parameter in the
ordered phase. An existing Monte Carlo calculation on the three-state
antiferromagnetic Potts model, which has the effective symmetry, is shown
to be consistent with the proposed scaling law. It strongly supports the
Renormalization-Group picture that there is a single massive ordered phase,
although an apparently rotationally symmetric region in the intermediate
temperature was observed numerically.Comment: 5 pages in REVTEX, 2 PostScript figure
Chiral exponents in O(N) x O(m) spin models at O(1/N^2)
The critical exponents corresponding to chirality are computed at O(1/N^2) in
d-dimensions at the stable chiral fixed point of a scalar field theory with an
O(N) x O(m) symmetry. Pade-Borel estimates for the exponents are given in three
dimensions for the Landau-Ginzburg-Wilson model at m = 2.Comment: 8 latex page