Nodal-Chain Semimetal States and Topological Focusing in Phononic Crystals

作者：Lu, Jiuyang; Huang, Xueqin; Yan, Mou; Li, Feng^*; Deng, Weiyin^*; Liu, Zhengyou^*

来源：Physical Review Applied, 2020, 13(5): 054080.

DOI：10.1103/PhysRevApplied.13.054080

We report the realization of a semimetal state in a phononic crystal, which hosts nodal-chain degeneracy in momentum space. The nodal-chain dispersion consists of interconnecting degenerate lines, and is protected by the nonsymmorphic and time-reversal symmetries together. The nontrivial Zak phases, induced by the nodal-chain configuration, give rise to the nonleaky drumhead surface modes on the surfaces. When the nonsymmorphic symmetry is broken, the nodal-chain semimetal transits to valley insulating state. The valley interface states present on the interface of two distinct valley phases, by which a topological focusing, which is free from reflection, is demonstrated. These findings enrich the knowledge of nodal-line materials and may pave the way to innovative acoustic devices.

• 单位
  武汉大学