Higher-order topological crystalline insulating phase and quantized hinge charge in topological electride apatite
Higher-order topological crystalline insulating phase and quantized hinge charge in topological electride apatite
复制标题
DOI：
10.1103/physrevresearch.2.043131
复制
发表时间：
2020-04
期刊：
影响因子：
--
通讯作者：
M. Hirayama;R. Takahashi;S. Matsuishi;H. Hosono;S. Murakami
中科院分区：
文献类型：
--
作者：
M. Hirayama;R. Takahashi;S. Matsuishi;H. Hosono;S. Murakami
在高阶拓扑绝缘体中，体电子态和表面电子态是有间隙的，但存在受空间对称性保护的无间隙铰链态。在这里，我们通过从头计算表明，La磷灰石是一种高阶拓扑晶体绝缘体。它是一维电子，其中沿着c轴的一维间隙空穴支撑着阴离子电子，并且这些一维沟道中的电子态可以很好地用一维Su-Schrieffer-Heeger模型来近似。当晶体解理成六角棱柱时，120个铰链支持无间隙铰链态，其填充量子化为2/3。这种填充量子化来自于拓扑起源。我们发现，填充量的量化值取决于构成晶体的基本块。磷灰石由三角形块组成，这对在铰链上提供非平凡的分数电荷至关重要。
In higher-order topological insulators, bulk and surface electronic states are gapped, while there appear gapless hinge states protected by spatial symmetry. Here we show by ab initio calculations that the La apatite electride is a higher-order topological crystalline insulator. It is a one-dimensional electride, in which the one-dimensional interstitial hollows along the $c$ axis support anionic electrons, and the electronic states in these one-dimensional channels are well approximated by the one-dimensional Su-Schrieffer-Heeger model. When the crystal is cleaved into a hexagonal prism, the 120$^\circ$ hinges support gapless hinge states, with their filling quantized to be 2/3. This quantization of the filling comes from a topological origin. We find that the quantized value of the filling depends on the fundamental blocks that constitute the crystal. The apatite consists of the triangular blocks, which is crucial for giving nontrivial fractional charge at the hinge.