Spin-Peierls transition of the first order in S=1 antiferromagnetic Heisenberg chains - art. no. 014405

We investigate a one;dimensional S = 1 antiferromagnetic Heisenberg model c oupled to a lattice distortion by a quantum Monte Carlo method. Investigati ng the ground-state energy of the static bond-alternating chain, we find th at the instability to a dimerized chain depends on the value of the spin-ph onon coupling, unlike the case of S - 1/2. The spin state is the dimer stat e or the uniform Haldane state depending on whether the lattice distorts or not, respectively. At an intermediate value of the spin-phonon coupling, w e find the first-order transition between the two states. We also find the coexistence of the two states.