Gate-tunable chiral phonons in low-buckled group-IVA monolayers

TL;DR

This study demonstrates that applying an electric field to low-buckled group-IVA monolayers can control chiral phonons by opening a phononic gap and reversing phonon chirality, enabling new phononic and valley device functionalities.

Contribution

It reveals electric field tuning of chiral phonons in group-IVA monolayers, showing how to manipulate phonon properties for potential device applications.

Findings

Electric field opens a phononic gap at high-symmetry points.

Phonon chirality can be reversed by changing field direction.

Chiral phonons exhibit robust polarization and pseudoangular momentum.

Abstract

We investigate the electric response of chiral phonons on the low-buckled group-IVA monolayers by performing first-principles calculations. The vertical electric field breaks the degeneracy of phonon modes at high-symmetry $\pm K$ points of the phonon Brillouin zone, and the size of the phononic gap is proportional to the strength of the electric field. The gapped phonon modes at $\pm K$ possess chiralities with considerable phonon circular polarizations and discrete phonon pseudoangular momenta. The chiralities of phonons are robust against the variation of the field strength, but reversed by changing the field direction. Electric control of chiral phonons adds a new dimension to the study of chiral phonons, which has potential use in the design of phononic and valley devices.