Abnormal topological refraction into free medium at subwavelength scale in valley phononic crystal plates

Linyun Yang, Kaiping Yu, Bernard Bonello*, Bahram Djafari-Rouhani, Wei Wang, Ying Wu

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

18 Citations (Scopus)


In this work we propose a topological valley phononic crystal plate and we extensively investigate the refraction of valley modes into the surrounding homogeneous medium. This phononic crystal includes two sublattices of resonators (A and B) modeled by mass-spring systems. We show that two edge states confined at the AB/BA and BA/AB type domain walls exhibit different symmetries in physical space and energy peaks in the Fourier space. As a result, distinct refraction behaviors, especially through an armchair cut edge, are observed. On the other hand, the decay depth of these localized topological modes, which is found to be solely determined by the relative resonant strength between the scatterers, significantly affects the refraction patterns. More interestingly, the outgoing traveling wave through a zigzag interface becomes evanescent when operating at deep subwavelength scale. This is realized by tuning the average resonant strength. We show that the evanescent modes only exist along a particular type of outlet edge and that they can couple with both topological interface states. We also present a near-ideal monopole and a dipole emitter based on our phononic structure.

Original languageEnglish
Article number184303
JournalPhysical Review B
Issue number18
Publication statusPublished - 6 May 2021

Scopus Subject Areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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