Properties of the two-dimensional spin-1/2 Heisenberg model on a honeycomb lattice with interlayer coupling

The magnetic properties of the two-dimensional S=1/2 (quantum) antiferromagnetic Heisenberg model on a honeycomb lattice with and without interlayer coupling are studied by means of a continuous Euclidean time Quantum Monte-Carlo algorithm. The internal energy, the magnetic susceptibility and the staggered magnetization are determined in the full temperature range. For the two-dimensional system the ground-state energy/bond is found to be E0hc=-0.36303(13), and the zero temperature staggered magnetization mst=0.2681(8). For coupled planes of honeycomb systems a phase transition from an ordered phase to a disordered phase is found at T/J=0.695(10)