Progress of Theoretical Physics Supplement
Spin-Peierls Transition inS=1 Antiferromagnetic Heisenberg Chains
Hiroaki Onishi, Seiji Miyashita
Abstract
We investigate a one-dimensional S=1 antiferromagnetic Heisenberg model coupled to lattice distortion by a quantum Monte Carlo method. The instability to a dimerized chain in the ground state depends on the value of the elastic constant, unlike the case of S=1/2. We find the first-order transition between a uniform Haldane state and a dimerized state. The two non-magnetic states coexist in the ground state and a domain-wall structure is observed.