论文标题
III型Dirac锥来自退化的定向平坦带：分子轨道表示的观点
Type-III Dirac Cones from Degenerate Directionally Flat Bands: Viewpoint from Molecular-Orbital Representation
论文作者
论文摘要
我们提出了一种系统的方法，可以从退化的定向扁平带中创建III型狄拉克锥。在这里，方向平坦的频带仅在一定方向上完全无分散带。关键策略是通过添加具有选定形式的汉密尔顿矩阵形式的扰动来保留一个定向平坦的带。通过使用我们开发的“分子 - 轨道表示”来描述这种形式的扰动形式。因此，即使没有微调跳跃参数，这些模型即使没有微调参数也获得了宿主类型的dirac锥。为了证明这种方法的普遍性，我们研究了两个波段模型和四波段模型的具体实例。
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.
