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arXiv 2008.09974cond-mat.str-elmath-phmath.MP
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自旋S=1/2反铁磁海森堡模型中的多自旋子激发

Multispinon excitations in the spin S=1/2 antiferromagnetic Heisenberg model

Yu-Liang Liu

摘要:

利用自旋算符的对易关系,首先写出自旋磁化率的运动方程和相关的具有层次结构的关联函数,然后在“软截止”近似下,给出自旋S=1/2反铁磁海森堡模型的自旋磁化率运动方程,这与系统在低能量/温度极限中是否具有长程序无关。通过求解这组方程,我们分别应用于链、正方形格子和蜂窝格子,得到了低激发的上、下界。对于一个链,低激发的上下边界与Bethe不等式得到的精确边界相同,其中基元激发是自旋对。对于正方形晶格,自旋波激发(磁振子)驻留在靠近低位激发的最低边界的区域中,并且多自旋子激发发生在靠近低位激发的上边界的高能区域中。对于蜂窝晶格,我们有一种“模式”的低位激发。本文的结果符合Lieb-Schultz-Mattis定理,并且与最近的中子散射观测和正方形晶格的数值模拟结果一致。

英文摘要:

With the commutation relations of the spin operators, we first write out the equations of motion of the spin susceptibility and related correlation functions that have a hierarchical structure, then under the "soft cut-off" approximation, we give a set of equations of motion of spin susceptibilities for a spin S=1/2 antiferromagnetic Heisenberg model, that is independent of whether or not the system has a long range order in the low energy/temperature limit. Applying for a chain, a square lattice and a honeycomb lattice, respectively, we obtain the upper and the lowest boundaries of the low-lying excitations by solving this set of equations. For a chain, the upper and the lowest boundaries of the low-lying excitations are the same as that of the exact ones obtained by the Bethe ansatz, where the elementary excitations are the spinon pairs. For a square lattice, the spin wave excitation (magnons) resides in the region close to the lowest boundary of the low-lying excitations, and the multispinon excitations take place in the high energy region close to the upper boundary of the low-lying excitations. For a honeycomb lattice, we have one kind of "mode" of the low-lying excitation. The present results obey the Lieb-Schultz-Mattis theorem, and they are also consistent with recent neutron scattering observations and numerical simulations for a square lattice.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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