论文标题
莫尔斯（Morse
Morse theory study on the evolution of nodal lines in $\mathcal{PT}$-symmetric nodal-line semimetals
论文作者
论文摘要
节点线半学是一个无拓扑间相，其中包含称为淋巴结线的一维归化性。淋巴结线因压力等系统的持续变化而变形，甚至可以改变拓扑结构，但是尚未系统地理解淋巴结线拓扑的变化是什么样的。在本文中，我们通过Morse理论对节点线变化的拓扑变化事件进行了分类，并揭示了在无自旋的淋巴结线环境中可以通过反转和时间倒流对称性保护淋巴结线的三种类型的拓扑变化，即创建，重新连接和歼灭。它们的特征是索尔斯理论中上述三种类型的索引具有0、1和2的索引。此外，我们将理论扩展到具有旋转对称性和镜像对称性的系统，并揭示了每个对称性下节点线的拓扑变化的可能事件。
A nodal-line semimetal is a topological gapless phase containing one-dimensional degeneracies called nodal lines. The nodal lines are deformed by a continuous change of the system such as pressure and they can even change their topology, but it is not systematically understood what kind of changes of topology of nodal lines are possible. In this paper, we classify the events of topology change of nodal lines by the Morse theory and reveal that only three types of topology changes of nodal lines, i.e., creation, reconnection, and annihilation, are possible in the spinless nodal-line semimetal protected by inversion and time-reversal symmetries. They are characterized by an index having the values 0, 1, and 2 for the above three types in the Morse theory. Moreover, we extend our theory to systems with rotational symmetries and mirror symmetry and disclose the possible events of topology change of nodal lines under each symmetry.
