Hubbard模型在Kagome晶格上的磁有序相研究

论文摘要

量子自旋液体（QSL）是当前凝聚态领域的热点之一,它对于理解高温超导机理有着重要的意义。目前,量子自旋液体最有可能出现三角晶格、在蜂窝晶格、Kagome晶格中。Kagome晶格具有强烈的几何阻挫和量子涨落,是发现量子自旋液体最理想的材料结构,其基本性质十分具有研究意义。然而对于kagome晶格在范霍夫填充附近的电子有序相,在采用pFRG和SMFRG的计算结果之间,关于较大互作用U下是否会出现FM序存在争议。在本文中,我们采用了RPA近似和平均场近似的方法,研究了kagome晶格模型在1/6空穴掺杂附近的磁有序相。我们的结果说明,Kagome晶格自旋系统只有在U<U0≈1.5t时,才会出现铁磁序,而在U>U0时,系统会随着温度降低,出现120°-AFM序。随着U的增大,系统的相变温度也逐渐升高。在绪论中,我们简要介绍了量子自旋液体,并推导了Hubbard模型哈密顿量。第二章介绍了kagome晶格的构形,及其紧束缚能带和态密度。在第三章中,我们首先给出了RPA修正后的磁化率计算式,然后展示了Kagome晶格的铁磁和反铁磁失稳曲线。第四章首先推导了Kagome晶格的平均场近似哈密顿量和序参量的迭代方程,然后展示了能带图和磁性相图,并与动力学平均场计算的结果做了比较。在第五章中,我们对全文进行了总结。

论文目录

文章来源

类型: 硕士论文

作者: 刘振

导师: 王强华

关键词: 晶格,模型,平均场近似,失稳

来源: 南京大学

年度: 2019

分类: 基础科学

专业: 物理学

单位: 南京大学

分类号: O469

总页数: 42

文件大小: 2796K

下载量: 98

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