Type-III Dirac Cones from Degenerate Directionally Flat Bands: Viewpoint from Molecular-Orbital Representation
Type-III Dirac Cones from Degenerate Directionally Flat Bands: Viewpoint from Molecular-Orbital Representation
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DOI：
10.7566/jpsj.89.103704
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发表时间：
2020-10-15
影响因子：
1.7
通讯作者：
Hatsugai, Yasuhiro
中科院分区：
文献类型：
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作者：
Mizoguchi, Tomonari;Hatsugai, Yasuhiro
我们提出了一种从简并的方向平坦带中产生III型狄拉克锥体的系统方法。这里，方向平坦的频带指的是只在某一方向上完全无色散的频带。关键策略是通过添加具有选定形式的哈密顿矩阵的扰动来保留其中一个方向平坦的频带，同时使另一个频带具有色散。这种形式的微扰是通过使用我们开发的描述平带模型的“分子轨道表示”来发现的。因此，即使在没有微调跳跃参数的情况下，模型也可以获得宿主III型狄拉克锥体。为了证明这种方法的普遍性，我们研究了两带模型和四带模型的具体例子。
We present a systematic method of creating type-III Dirac cones from degenerate directionally flat bands. Here, the directionally flat band means a completely dispersionless band only in a certain direction. The key strategy is to retain one of the directionally flat bands while making the other dispersive, by adding a perturbation having a selected form of a Hamiltonian matrix. Such a form of a perturbation is found by using the "molecular-orbital representation" which we have developed to describe flat-band models. The models thus obtained host type-III Dirac cones even without fine-tuning hopping parameters. To demonstrate the ubiquity of this method, we study concrete examples of two-band models and a four-band model.