We consider the effects of random fluctuations in the local geometry on the ground-state properties of a two-dimensional quantum antiferromagnet. We analyze the behavior of spins described by the Heisenberg model as a function of what we call phason disorder, following a terminology used for aperiodic systems. The calculations were carried out both within linear spin-wave theory and using quantum Monte Carlo simulations. An “order by disorder” phenomenon is observed in this model, wherein antiferromagnetism is found to be enhanced by phason disorder. The value of the staggered order parameter increases with the number of defects, accompanied by an increase in the ground-state energy of the system.

• Received 10 November 2011

DOI:https://doi.org/10.1103/PhysRevB.85.094434