Observation of hourglass nodal lines in photonics

Research output: Contribution to journalArticlepeer-review

Authors

  • Lingbo Xia
  • Qinghua Guo
  • Biao Yang
  • Jiaguang Han
  • Chao-xing Liu
  • Weili Zhang

Colleges, School and Institutes

Abstract

Nodal line semimetals exhibiting line degeneracies in three-dimensional momentum space have been demonstrated recently. In general, the presence of nodal line semimetals is protected by special symmetries, such as mirror symmetry. However, these symmetries are usually necessary but not sufficient conditions, as nodal lines can be annihilated even without breaking them. Very recently, nodal line semimetal possessing an hourglass-shaped band structure emerges as a more robust candidate, where line degeneracies cannot be annihilated while preserving all underlying spatial symmetries. Here, for the first time, we experimentally demonstrate the presence of an hourglass nodal line (HNL) in photonic metacrystal at microwave frequency. We observe the HNL through near-field scanning of the spatial fields, followed by subsequent Fourier transformations. The observed photonic HNL resides in a clean and large frequency interval and is immune to symmetry preserving perturbation, which provides an ideal robust platform for photonic applications, such as anomalous quantum oscillation, spontaneous emission and resonant scattering.

Details

Original languageEnglish
Article number103903
Number of pages6
JournalPhysical Review Letters
Volume122
Issue number10
Publication statusPublished - 15 Mar 2019