手性晶体 CsBe$_2$F$_5$ 中多种类型的非常规准粒子
Multiple types of unconventional quasiparticles in the chiral crystal CsBe$_2$F$_5$
AI总结：
本文通过第一性原理计算与对称性分析，揭示手性晶体 CsBe$_2$F$_5$ 声子谱中多种非常规拓扑准粒子共存及其对称性保护机制，为相关物理研究提供了材料平台。
摘要：
非常规拓扑准粒子近年来在凝聚态物理领域引起了广泛关注。在此，基于第一性原理计算和对称性分析，我们揭示了手性晶体 CsBe$_2$F$_5$ 的声子谱中多种有趣的非常规拓扑准粒子共存。具体而言，我们在 CsBe$_2$F$_5$ 中识别出八条纠缠的声子带，它们产生了多种非常规拓扑准粒子，包括自旋-1 Weyl 点、电荷-2 Dirac 点、节面和沙漏型节线环。我们证明了这些非常规拓扑准粒子受到晶体对称性的保护。我们展示了在 (001) 表面上存在两条大的费米弧，它们连接体态自旋-1 Weyl 点和电荷-2 Dirac 点的投影，并横跨整个表面布里渊区。我们的工作不仅阐明了手性晶体引人入胜的拓扑性质，还为探索与多种类型非常规拓扑准粒子相关的迷人物理提供了一个优异的材料平台。
英文摘要：
Unconventional topological quasiparticles have recently garnered significant attention in the realm of condensed matter physics. Here, based on first-principles calculations and symmetry analysis, we reveal the coexistence of multiple types of interesting unconventional topological quasiparticles in the phonon spectrum of the chiral crystal CsBe$_2$F$_5$. Specifically, we identified eight entangled phonon bands in CsBe$_2$F$_5$, which give rise to various unconventional topological quasiparticles, including the spin-1 Weyl point, the charge-2 Dirac point, the nodal surface, and the hourglass nodal loop. We demonstrate that these unconventional topological quasiparticles are protected by crystal symmetry. We show that there are two large Fermi arcs connecting projections of the bulk spin-1 Weyl point and charge-2 Dirac point on the (001) surface and across the entire surface Brillouin zone. Our work not only elucidates the intriguing topological properties of chiral crystals but also provides an excellent material platform for exploring the fascinating physics associated with multiple types of unconventional topological quasiparticles.
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