74,919 research outputs found
A New Method of Calculating the Spin-Wave Velocity of Spin-1/2 Antiferromagnets With Symmetry in a Monte Carlo Simulation
Motivated by the so-called cubical regime in magnon chiral perturbation
theory, we propose a new method to calculate the low-energy constant, namely
the spin-wave velocity of spin-1/2 antiferromagnets with symmetry in
a Monte Carlo simulation. Specifically we suggest that can be determined by
when the squares of the spatial and temporal winding numbers are
tuned to be the same in the Monte Carlo calculations. Here and are
the inverse temperature and the box size used in the simulations when this
condition is met. We verify the validity of this idea by simulating the quantum
spin-1/2 XY model. The obtained by using the squares of winding numbers is
given by which is consistent with the known values of in
the literature. Unlike other conventional approaches, our new idea provides a
direct method to measure . Further, by simultaneously fitting our Monte
Carlo data of susceptibilities and spin susceptibilities to
their theoretical predictions from magnon chiral perturbation theory, we find
is given by which agrees with the one we obtain by the
new method of using the squares of winding numbers. The low-energy constants
magnetization density and spin stiffenss of quantum spin-1/2
XY model are determined as well and are given by
and , respectively. Thanks to the prediction power of
magnon chiral perturbation theory which puts a very restricted constraint among
the low-energy constants for the model considered here, the accuracy of we present in this study is much precise than previous Monte Carlo result.Comment: 5 pages, 7 figure
Very High Precision Determination of Low-Energy Parameters: The 2-d Heisenberg Quantum Antiferromagnet as a Test Case
The 2-d spin 1/2 Heisenberg antiferromagnet with exchange coupling is
investigated on a periodic square lattice of spacing at very small
temperatures using the loop-cluster algorithm. Monte Carlo data for the
staggered and uniform susceptibilities are compared with analytic results
obtained in the systematic low-energy effective field theory for the staggered
magnetization order parameter. The low-energy parameters of the effective
theory, i.e.\ the staggered magnetization density , the spin stiffness , and the spin wave
velocity are determined with very high precision. Our study
may serve as a test case for the comparison of lattice QCD Monte Carlo data
with analytic predictions of the chiral effective theory for pions and
nucleons, which is vital for the quantitative understanding of the strong
interaction at low energies.Comment: 5 pages, 4 figures, 1 tabl
Investigation of a universal behavior between N\'eel temperature and staggered magnetization density for a three-dimensional quantum antiferromagnet
We simulate the three-dimensional quantum Heisenberg model with a spatially
anisotropic ladder pattern using the first principles Monte Carlo method. Our
motivation is to investigate quantitatively the newly established universal
relation near the quantum critical
point (QCP) associated with dimerization. Here , , and are
the N\'eel temperature, the spinwave velocity, and the staggered magnetization
density, respectively. For all the physical quantities considered here, such as
and , our Monte Carlo results agree nicely with the
corresponding results determined by the series expansion method. In addition,
we find it is likely that the effect of a logarithmic correction, which should
be present in (3+1)-dimensions, to the relation
near the investigated QCP only sets in significantly in the region
with strong spatial anisotropy.Comment: 5 pages, 7 figures, 2 table
Systematic Effective Field Theory Investigation of Spiral Phases in Hole-Doped Antiferromagnets on the Honeycomb Lattice
Motivated by possible applications to the antiferromagnetic precursor of the
high-temperature superconductor NaCoOyHO, we use a systematic
low-energy effective field theory for magnons and holes to study different
phases of doped antiferromagnets on the honeycomb lattice. The effective action
contains a leading single-derivative term, similar to the Shraiman-Siggia term
in the square lattice case, which gives rise to spirals in the staggered
magnetization. Depending on the values of the low-energy parameters, either a
homogeneous phase with four or a spiral phase with two filled hole pockets is
energetically favored. Unlike in the square lattice case, at leading order the
effective action has an accidental continuous spatial rotation symmetry.
Consequently, the spiral may point in any direction and is not necessarily
aligned with a lattice direction.Comment: 10 pages, 6 figure
- …