Pseudospins and topological effects of phonons in a Kekule lattice

TL;DR

This paper uncovers a new pseudospin concept for phonons in a Kekulé lattice, revealing topological effects like protected interface states and Hall effects, with broad implications for various particles.

Contribution

It introduces a novel pseudospin framework for phonons with quantized Berry phases, enabling new topological phenomena and control methods.

Findings

Discovery of phonon pseudospins with quantized Berry phases

Observation of topologically protected interface states

Demonstration of phonon pseudospin Hall effect

Abstract

The search for exotic topological effects of phonons has attracted enormous interest for both fundamental science and practical applications. By studying phonons in a Kekul\'e lattice, we find a new type of pseudospins characterized by quantized Berry phases and pseudoangular momenta, which introduces various novel topological effects, including topologically protected pseudospin-polarized interface states and a phonon pseudospin Hall effect. We further demonstrate a pseudospin-contrasting optical selection rule and a pseudospin Zeeman effect, giving a complete generation-manipulation-detection paradigm of the phonon pseudospin. The pseudospin and topology-related physics revealed for phonons is general and applicable for electrons, photons and other particles.