Numerical Solution of the spin-3/2 Heisenberg Antiferromagnetic Chains Using a Projector Method

An efficient projector method is used to calculate the energies of the ground state and the first excited state, and hence the energy gap between them, of the spin-3/2 Heisenberg antiferromagnetic chains with linear sizes up to N = 32. For the chains up to N = 8 the exact results are obtained, and for longer chains up to N = 32 they are estimated by imposing on Monte Carlo technique. It is found that the size dependence of the ground state energy per site has the form of eo(N) - eo] ～ 1/N², and the value of the ground state energy per site as N→∞ is eo = -2.8248. Our results show that the energy gap trends to zero as N→∞, which is consistent with the rigorous proof.