论文标题
二次带触摸系统中拓扑缺陷的颜色退化性
Color degeneracy of topological defects in quadratic band touching systems
论文作者
论文摘要
我们研究了在涡流和绝缘和超导质量的涡流中，研究二维费米二次带触摸（QBT）系统。此类系统的原型示例是Bernal双层石墨烯，该石墨烯在具有必要的u（1）对称性的质量涡流的情况下支持八种零能量模式。在涡流核心内，通过分别以五个和十种不同的方式将其SO（4）和SU（4）和SU（2）手性对称性分配零模式，可以通过以五种和十种方式将零模式分解为零模式来发展局部期望值。特别是，每个SU（2）手性对称性可以通过手性 - 三个质量秩序的三个不同的副本打破，从而产生了竞争订单中颜色或风味退化的概念。相比之下，除通常的概括性U（1）电荷外，三个抗强制性质量的天空为其核心支撑了六个质量，并且具有SU（2）Isospin量子数。因此，$ 4E $ kekule配对密度波可以在Néel层抗fiferromagnet的Skyrmion核心中发展，而Skyrmion的量子旋转厅绝缘子还支持平凡的$ s $ - 波配对。我们还分析了仅支持QBT副本的核心板或Kagome晶格上这些缺陷核心中竞争订单的内部代数。
We study two-dimensional fermionic quadratic band touching (QBT) systems in the presence of vortex and skyrmion of insulating and superconducting masses. A prototypical example of such systems is the Bernal bilayer graphene that supports eight zero-energy modes in the presence of a mass vortex with the requisite U(1) symmetry. Inside the vortex core, additional ten masses that close an SO(5) algebra can develop local expectation values by splitting the zero modes in five and ten different ways by lifting its SO(4) and SU(2) chiral symmetries, respectively. In particular, each SU(2) chiral symmetry can be broken by three distinct copies of chiral-triplet mass orders, giving rise to the notion of the color or flavor degeneracy among the competing orders. By contrast, a skyrmion of three anticommuting masses supports additional six masses in its core, and possesses an SU(2) isospin quantum number, besides the usual generalized U(1) charge. Consequently, charge $4e$ Kekule pair-density-waves can develop in the skyrmion core of Néel layer antiferromagnet, while a skyrmion of quantum spin Hall insulator in addition supports a mundane $s$-wave pairing. We also analyze the internal algebra of competing orders in the core of these defects on checkerboard or Kagome lattice that supports only a single copy of QBT.
