一个准一维耦合自旋三角形的耦合集团处理
Coupled cluster treatment of one quasi-one-dimensional coupled spin triangles
摘要：
利用耦合集团方法（CCM）和数值精确对角化（ED）方法，研究了准一维耦合自旋三角形的性质。ED结果表明，当a<ac 1时，体系处于严格的四聚体-二聚体（TD）态。我们证明了在该参数范围内利用CCM可以形成精确的TD态。更有趣的是，我们发现通过CCM也可以得到TD态的精确自旋能隙。在临界点ac 1处，发生一级跃迁，系统的基态从TD态演化到铁磁长程序态。在a> ac 1的参数范围内，CCM对基态能、磁化强度和反铁磁能隙等物理量的计算结果与ED的结果吻合得很好，因此CCM可以用来精确地分析整个参数范围内准一维耦合自旋三角形的性质.我们相信它也可以可靠地应用于研究其他准单自旋系统的性质。
英文摘要：
By using the coupled cluster method (CCM) and the numerical exact diagonalization (ED) method, we investigated the properties of the one quasi-one-dimensional coupled spin triangles. The results of ED disclose that the system is in the exact tetramer-dimer (TD) state if a<ac1 . We prove that the exact TD state can be formed by using CCM in that parameter region. It is more interesting to find that the exact spin gap in the TD state can also be obtained via CCM. At the critical point ac1, a first order transition occurs and the ground state of the system evolves from the TD state to the ferromagnetic long range order state. In the parameter region a>ac1, we find that CCM results for some physical quantities, such as the ground state energy, the magnetization and the antiferromagnetic gap are in excellent agreement with the results obtained by ED. Thus, CCM can be used to accurately analyze the properties of the quasi-one-dimensional coupled spin triangles in the whole parameter region. We believe that it can also be applied to investigating the properties of other quasi-one spin systems reliably.
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