论文标题
拓扑和非亲本金属中的三重变性淋巴结线
Triply degenerate nodal lines in topological and non-topological metals
论文作者
论文摘要
拓扑结节线半学表现出受对称性保护的双重或四倍的退化淋巴结线。在这里，我们研究了金属中存在三重变性淋巴结线的可能性。我们提出了两种类型的三级变性淋巴结线，一种在拓扑上很琐碎，另一种是非平凡的。第一种类型是由二维假蛋白-1费米子堆叠在一起的，可以将其视为可调带跨线结构的关键案例，其中包含一个对称性保护的二次跨带串线和非脱位频带，并且可以分成四个在扰动下分为四个Weyl nodal线。我们发现节点线结构的表面状态取决于晶格的几何形状和表面终止。这样的金属在一系列填充范围内具有费米表面的嵌套，当包括相互作用时，导致密度波状态。第二种是假蛋白-1费米子的涡流环。在该系统中，伪旋转形成了天空质纹理，并且表面状态是完全扩展的拓扑式费米弧，因此该模型表现出3D量子异常的大厅效应，具有最大的霍尔电导率。涡流环可以演变成一对在第一个布里群区域中未关闭的涡流线。如果它是系统的唯一淋巴结功能，则在晶格模型中不能单独存在涡流行。
Topological nodal-line semimetals exhibit double or fourfold degenerate nodal lines, which are protected by symmetries. Here, we investigate the possibility of the existence of triply degenerate nodal lines in metals. We present two types of triply degenerate nodal lines, one topologically trivial and the other nontrivial. The first type is stacked by two-dimensional pseudospin-1 fermions, which can be viewed as an critical case of a tunable band-crossing line structure that contains a symmetry-protected quadratic band-crossing line and a non-degenerate band, and can split into four Weyl nodal lines under perturbations. We find that surface states of the nodal line structure are dependent on the geometry of the lattice and the surface termination. Such a metal has a nesting of Fermi surface in a range of filling, resulting in a density-wave state when interaction is included. The second type is a vortex ring of pseudospin-1 fermions. In this system, the pseudospins form Skyrmion textures, and the surface states are fully extended topological Fermi arcs so that the model exhibits 3D quantum anomalous Hall effect with a maximal Hall conductivity. The vortex ring can evolve into a pair of vortex lines that are not closed in the first Brillouin zone. A vortex line cannot singly exist in the lattice model if it is the only nodal feature of the system.
