1202.1057 (M. -T. Kao et al.)

Quantum phase transitions of 2-d dimerized spin-1/2 Heisenberg models
with spatial anisotropy    [PDF]

M. -T. Kao, D. -J. Tan, F. -J. Jiang

Motivated by the unexpected Monte Carlo results as well as the theoretical
proposal of a large correction to scaling for the critical theory of the 2-d
staggered-dimer spin-1/2 Heisenberg model on the square lattice, we study the
phase transitions induced by dimerization of several dimerized quantum
Heisenberg models with spatial anisotropy using first principles Monte Carlo
method. We focus on investigating the finite-size scaling of the observables
$\rho_{s1}2L$ and $\rho_{s2}2L$ since such strategy might reveal the subtlety
of determining the corresponding critical theory. Here, $\rho_{si}$ with $i \in
{1,2}$ and $L$ refer to the spin stiffness in the $i$ direction and the spatial
box size used in the simulations, respectively. Remarkably, while the Monte
Carlo data we obtain for all the models considered here, including the
herringbone- and ladder-dimer models on the square lattice, seem to be
compatible with the recently proposed scenario of an enhanced correction to
scaling, our data are in consistence with the established numerical values for
the critical exponents in the O(3) universality class as well. To explain the
results presented in this study, a more detailed numerical study, and possibly
a better theoretical understanding, for the critical theories of the models
investigated here is required.

View original: http://arxiv.org/abs/1202.1057