Topological nodal-line phonons from accidental degeneracy of double bands

作者：Zijuan Xie, Yuanjun Jin, Xiaoliang Xiao, Zhongjia Chen, Jijun Zhao · 发表于：Physical review. B./Physical review. B · 年份：2025 · DOI：10.1103/ft3y-rlcz · 被引用次数：1 · 研究领域：Topological Materials and Phenomena、Quasicrystal Structures and Properties、2D Materials and Applications

Significant progress has been achieved in the classification of topological quasiparticles after the accomplishment of large-scale searches for topological materials. However, some degeneracies in the current classification may actually lie on extended degeneracy manifolds, suggesting that a more refined classification is required. Here, we investigate accidental degeneracies of double bands (ADDBs) along high-symmetry lines in phononic systems and propose a refined classification that distinguishes the charge-0, charge-2 Dirac point, and point in nodal line (PiNL). By analyzing the symmetry constraints through group theory and compatibility relations, we identify all three types of ADDBs (charge-0, charge-2 Dirac point, and PiNL) across all space groups and high-symmetry lines. First-principles calculations on ${\mathrm{FeP}}_{2}$ confirm the existence of topological nodal-line phonons from ADDBs in realistic phononic materials. This work enriches our understanding of the diverse manifestations of quasiparticle excitations in topological phonon systems.