Strain Tunable Phononic Topological Bandgaps in Two-Dimensional Hexagonal Boron Nitride

TL;DR

This study shows that in two-dimensional hexagonal boron nitride, topological phononic bandgaps are robust against strain but can be effectively tuned in frequency through biaxial strain, enabling flexible control of phononic properties.

Contribution

It is the first to demonstrate strain-induced tunability of topological phononic bandgaps in 2D hexagonal boron nitride, combining lattice dynamical calculations and molecular dynamics simulations.

Findings

Topologically protected phononic bandgaps remain open under severe deformation.

Biaxial strains can efficiently tune the position of the phononic bandgap.

Topological phonons are robust against mechanical strain effects.

Abstract

The field of topological mechanics has recently emerged due to the interest in robustly transporting various types of energy in a flaw and defect-insensitive fashion. While there have been a significant number of studies based on discovering and proposing topological materials and structures, very few have focused on tuning the resulting topological bandgaps, which is critical because the bandgap frequency is fixed once the structure has been fabricated. Here, we perform both lattice dynamical calculations and molecular dynamical simulations to investigate strain effects on the phononic topological bandgaps in two-dimensional monolayer hexagonal boron nitride. Our studies demonstrate that while the topologically protected phononic bandgaps are not closed even for severely deformed hexagonal boron nitride, and are relatively insensitive to uniaxial tension and shear strains, the position of the frequency gap can be efficiently tuned in a wide range through the application of biaxial strains. Overall, this work thus demonstrates that topological phonons are robust against the effects of mechanical strain engineering, and sheds light on the tunability of the topological bandgaps in nanomaterials.