Abstract
We use quantum Monte Carlo simulations to study effects of disorder on the quantum phase transition occurring versus the ratio in square-lattice dimerized Heisenberg antiferromagnets with intradimer and interdimer couplings and . The dimers are either randomly distributed (as in the classical dimer model), or come in parallel pairs with horizontal or vertical orientation. In both cases the transition violates the Harris criterion, according to which the correlation-length exponent should satisfy . We do not detect any deviations from the three-dimensional O(3) universality class obtaining in the absence of disorder (where ). We discuss special circumstances which allow for the type of disorder considered here.
- Received 7 June 2010
DOI:https://doi.org/10.1103/PhysRevB.82.172409
©2010 American Physical Society