论文标题
T-烯键的轨道敏感性：高阶范霍夫奇异性和狄拉克锥的相互作用
Orbital susceptibility of T-graphene: Interplay of high-order van Hove singularities and Dirac cones
论文作者
论文摘要
方形晶格是对四维材料（例如四维材料）的描述的基础。在本文中，我们表明，方形晶格的紧密结合模型包含常规和高级范霍夫点。特别是，该模型的光谱沿着由高阶鞍点组成的某些方向包含平坦线。通过计算电子的轨道敏感性来分析它们的作用。我们发现，状态密度中不同种类的范霍夫奇异性的存在会导致强烈的反应：普通奇点的顺磁性，对于高阶奇异性而言更为复杂。结果表明，轨道敏感性与跳高比$α$的函数揭示了$α\ $α\约0.94 $的顺磁相变。这是由于高阶VHS的顺磁性贡献的竞争和狄拉克锥的Dimagnetic贡献的竞争。将紧密结合模型的结果与三个频段接触点附近的低能有效伪-1模型进行了比较。
Square-octagon lattice underlies the description of a family of two-dimensional materials such as tetragraphene. In the present paper we show that the tight-binding model of square-octagon lattice contains both conventional and high-order van Hove points. In particular, the spectrum of the model contains flat lines along some directions composed of high-order saddle points. Their role is analyzed by calculating orbital susceptibility of electrons. We find that the presence of van Hove singularities of different kinds in the density of states leads to strong responses: paramagnetic for ordinary singularities and more complicated for high-order singularities. It is shown that the orbital susceptibility as a function of hoppings ratio $α$ reveals the dia- to paramagnetic phase transition at $α\approx 0.94$. This is due to the competition of paramagnetic contribution of high-order VHS and diamagnetic contribution of Dirac cones. The results for the tight-binding model are compared with low-energy effective pseudospin-1 model near the three band touching point.
