Electrically Controllable Chiral Phonons in Ferroelectric Materials

Chiral phonons have attracted increasing attention, as they play important roles in many different systems and processes. However, a method to control phonon chirality by external fields is still lacking. Here, we propose that in displacement-type ferroelectric materials, an external electric field can reverse the chirality of chiral phonons via ferroelectric switching. Using first-principles calculations, we demonstrate this point in the well known two-dimensional ferroelectric In$_2$Se$_3$. This reversal may lead to a number of electrically switchable phenomena, such as chiral phonon induced magnetization, phonon Hall effect, and possible interface phonon modes at ferroelectric domain boundaries. Our work offers a new way to control chiral phonons, which could be useful for the design of thermal or information devices based on them.