摘要
The bipartite entanglement of the two- and three-spin Heisenberg model was investigated by using the concept of negativity. It is found that for the ground-state entanglement of the two-spin model, the negativity always decreases as B increases if △ 〈γ- 1, and it may keep a steady value of 0.5 in the region of B 〈 J[（△＋ 1）2 -γ^2]^1/2 if △ 〉γ-1, while for that of the three-spin model, the negativity exhibits square wave structures if γ=0 or△=0. For thermal states, there are two areas showing entanglement, namely, the main region and the sub-region. The main region exists only when △ 〉 △c （△c =γ- 1 and （γ^2 - 1）/2 for the 2- and 3-spin model respectively） and extends in terms of B and T as A increases, while the sub-region survives only when γ≠0 and shrinks in terms of B and T as △ increases.
The bipartite entanglement of the two- and three-spin Heisenberg model was investigated by using the concept of negativity. It is found that for the ground-state entanglement of the two-spin model, the negativity always decreases as B increases if △ 〈γ- 1, and it may keep a steady value of 0.5 in the region of B 〈 J[（△＋ 1）2 -γ^2]^1/2 if △ 〉γ-1, while for that of the three-spin model, the negativity exhibits square wave structures if γ=0 or△=0. For thermal states, there are two areas showing entanglement, namely, the main region and the sub-region. The main region exists only when △ 〉 △c （△c =γ- 1 and （γ^2 - 1）/2 for the 2- and 3-spin model respectively） and extends in terms of B and T as A increases, while the sub-region survives only when γ≠0 and shrinks in terms of B and T as △ increases.
基金
National Natural Science Foundation of China(10547008)
