Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
Phys Rev Lett. 2018 Jun 15;120(24):240401. doi: 10.1103/PhysRevLett.120.240401.
The recent discovery of triply degenerate points (TDPs) in topological materials has opened a new perspective toward the realization of novel quasiparticles without counterparts in quantum field theory. The emergence of such protected nodes is often attributed to spin-vector-momentum couplings. We show that the interplay between spin-tensor- and spin-vector-momentum couplings can induce three types of TDPs, classified by different monopole charges (C=±2, ±1, 0). A Zeeman field can lift them into Weyl points with distinct numbers and charges. Different TDPs of the same type are connected by intriguing Fermi arcs at surfaces, and transitions between different types are accompanied by level crossings along high-symmetry lines. We further propose an experimental scheme to realize such TDPs in cold-atom optical lattices. Our results provide a framework for studying spin-tensor-momentum coupling-induced TDPs and other exotic quasiparticles.
最近在拓扑材料中发现了三重简并点（TDP），为实现没有量子场论对应物的新型准粒子开辟了新视角。这种受保护节点的出现通常归因于自旋-矢量-动量耦合。我们表明，自旋张量-和自旋-矢量-动量耦合的相互作用可以诱导三种类型的 TDP，根据不同的磁单极电荷（C=±2，±1，0）进行分类。磁场可以将它们提升为具有不同数量和电荷的外尔点。同一类型的不同 TDP 通过表面上有趣的费米弧连接，不同类型之间的转变伴随着沿高对称线的能级交叉。我们进一步提出了一种在冷原子光学晶格中实现这种 TDP 的实验方案。我们的结果为研究自旋张量-动量耦合诱导的 TDP 和其他奇异准粒子提供了一个框架。
