UC Davis

Motivated by the geometry of spins in the materials SrCu2O3 and CaCu2O3, we study a two-layer, spin-half Heisenberg model, with nearest-neighbor exchange couplings J and alphaJ along the two axes in the plane and a coupling J(perpendicular to) perpendicular to the planes. We study these class of models using the stochastic series expansion quantum Monte Carlo simulations at finite temperatures and series expansion methods at T=0. The critical value of the interlayer coupling, J(perpendicular to)(c), separating the Neel ordered and disordered ground states, is found to follow very closely a square root dependence on alpha. Both T=0 and finite-temperature properties of the model are presented and the contrasting behavior of SrCu2O3 and CaCu2O3 are explained.