Phonons as a platform for non-Abelian braiding and its manifestation in layered silicates
Recent study provides evidence for new multi-gap topologies in phonon spectra of layered silicates.
Braiding within a group of phonon bands in layered silicates as function of strain, respecting sixfold symmetry (left) and breaking it (right).
Topological phases of matter have revolutionised the fundamental understanding of band theory and hold great promise for next-generation technologies such as low-power electronics or quantum computers. Single-gap topologies have been extensively explored, and a large number of materials have been theoretically proposed and experimentally observed. These ideas have recently been extended to multi-gap topologies with band nodes that carry non-Abelian charges, characterised by invariants that arise by the momentum space braiding of such nodes. We show that multi-gap topologies and the accompanying phase transitions driven by braiding processes can be readily observed in the bosonic phonon spectra of known monolayer silicates. The associated braiding process can be controlled by means of an electric field and epitaxial strain. Finally, we propose that the band inversion processes at the Γ point can be tracked by following the evolution of the Raman spectrum, providing a clear signature for the experimental verification of the band inversion accompanied by the braiding process.Phonons as a platform for non-Abelian braiding and its manifestation in layered silicates, Bo Peng, Adrien Bouhon, Bartomeu Monserrat and Robert-Jan Slager, Nature Communications 13, 423 (2022).