Non-conventional topological band properties and gapless helical edge states in elastic phononic waveguides with Kekulé distortion

Abstract

This study investigates the topological behavior of a continuous elastic phononic structure characterized by a 3-term Kekulé distortion. The elastic waveguide consists of a hexagonal unit cell whose geometric dimensions are intentionally perturbed according to a generalized Kekulé scheme. The resulting structure exhibits an effective Hamiltonian that resembles a quantum spin Hall system, hence suggesting that the waveguide can support helical topological edge states. Using first-principles calculations, we show the existence of nondegenerate pseudospin states and a very peculiar 6-lobe pseudospin texture and Berry curvature pattern. Important insights are also provided concerning the topological states in the Kekulé lattice, so far considered indistinguishable, and their critical role in enabling unique gapless edge states, typically not achievable in phononic systems.

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Cited by in corpus (5)

• Synthetic Kramers pair in phononic elastic plates and helical edge states on a dislocation interface
• Observations of symmetry induced topological mode steering in a reconfigurable elastic plate
• Weyl points and topological surface states in a three-dimensional elastic lattice
• Topologically invisible defects in chiral mirror lattices
• On the role of geometric phase in the dynamics of elastic waveguides