QUANTUM PHASE-TRANSITIONS IN 2D ANTIFERROMAGNETS

Quantum Monte Carlo results for the T = 0 order-disorder transition of two-dimensional dimerized quantum Heisenberg antiferromagnets are presented. For a two-layer model, with the dimers having one member sn each plane, the finite-size scaling of the staggered structure factor and the staggered susceptibility is consistent with the SD classical Heisenberg universality class, as required if the transition a's described by the 2+1-dimensional non-linear sigma-model. However, for models with the dimers in a single plane, the behavior does not appear to be consistent vith this universality class.