Exhaustive List of Topological Hourglass Band Crossings in 230 Space Groups

Magnetic hourglass fermions: from exhaustive symmetry conditions to high-throughput materials predictions

Many topological band crossings (BCs) have been predicted efficiently utilizing the symmetry properties of wave-functions at high-symmetry points. Among various BCs, the so-called hourglass BCs (with the low-energy excitations dubbed as hourglass fermions) are fascinating since they can be guaranteed to exist under specific symmetry conditions even without realistic calculations. Such novel property renders the theoretical prediction on magnetic topological metals with hourglass BC (being Weyl point, Dirac point, lying in nodal loop, and so on) independent on the calculation methods and only d…

1651个磁性空间群和528个磁性层群中的所有沙漏型玻色子激发

All hourglass bosonic excitations in the 1651 magnetic space groups and 528 magnetic layer groups

本文全面分类了1651个磁性空间群和528个磁性层群中的沙漏型玻色子激发，确定了必然存在该激发的群结构，并通过第一性原理计算验证了材料中的沙漏声子，为人工结构设计提供指导。

Spinless hourglass nodal-line semimetals

Nodal-line semimetals, one of the topological semimetals, have degeneracy along nodal lines where the band gap is closed. In many cases, the nodal lines appear accidentally, and in such cases it is impossible to determine whether the nodal lines appear or not, only from the crystal symmetry and the electron filling. In this paper, for spinless systems, we show that in specific space groups at $4N+2$ fillings ($8N+4$ fillings including the spin degree of freedom), presence of the nodal lines is required regardless of the details of the systems. Here, the spinless systems refer to crystals where…

Cat's cradle-like Dirac semimetals in layer groups with multiple screw axes: Application to 2D Borophene and Borophane

Recently, the crystal symmetry-protected topological semimetals have aroused extensive interests, especially for the nonsymmorphic symmetry-protected one. We list the possible nonmagnetic topological semimetals and develop their k.p Hamiltonian in all layer groups with multiple screw axes in the absence of spin-orbital coupling. We find a novel cat's cradle-like topological semimetal phase, which looks like multiple hourglass-like band structures staggered together. Furthermore, we propose the monolayer borophene and borophane with pmmn layer group as the first material class to realize such n…

Topological correspondence between magnetic space group representations

The past years have seen rapid progress in the classification of topological materials. These diagnostical methods are increasingly getting explored in the pertinent context of magnetic structures. We report on a general class of electronic configurations within a set of anti-ferromagnetic-compatible space groups that are necessarily topological. Interestingly, we find a systematic correspondence between these anti-ferromagnetic phases to necessarily nontrivial topological ferro/ferrimagnetic counterparts that are readily obtained through physically motivated perturbations. Addressing the exha…