arXiv:0912.3990 · Physical Review B
Critical entropy of quantum Heisenberg magnets on simple-cubic lattices
Stefan Weßel
Abstract
We analyze the temperature dependence of the entropy of the spin-1/2 Heisenberg model on the three-dimensional simple-cubic lattice, for both the case of antiferromagnetic and ferromagnetic nearest-neighbor exchange interactions. Using optimized extended ensemble quantum Monte Carlo simulations, we extract the entropy at the critical temperature for magnetic order from a finite-size scaling analysis. For the antiferromagnetic case, the critical entropy density equals $0.341(5){k}_{B}$, whereas for the ferromagnet, a larger value of $0.401(5){k}_{B}$ is obtained. We compare our simulation results to estimates put forward recently in studies assessing means of realizing the antiferromagnetic N\'eel state in ultracold fermion gases in optical lattices.