Ground-State Properties of S=1 Antiferromagnetic Heisenberg Chains with Bond Alternation

抄録

Ground-state properties of S=1 antiferromagnetic Heisenberg chains with bond alternation, Η=J, ∑ _i, {1-(-1)ⁱδ } S_i· S_i+1, are studied by a quantum Monte Carlo method. Spin correlation between chain ends on the open chain appears for δ <0.25, while it vanishes for δ ≥ 0.25. At δ ~= 0.25, the spin correlation length has a peak and the S=1/2 edge states for the open chain disappear. The fourfold degeneracy of the ground state of the open chain holds for δ <0.25, while it is removed for δ ≥ 0.25. All the results support the continuous phase transition at δ ~= 0.25 demonstrated in the previous works.