Phonons of electronic crystals in two-dimensional semiconductor moir\'e patterns

TL;DR

This paper investigates the phonon properties of various electronic crystal patterns in 2D semiconductor moiré systems, revealing stability differences and the emergence of chiral phonons with potential for topological phononic applications.

Contribution

It provides a theoretical analysis of phonon dispersions in different moiré crystal structures, highlighting the conditions for chiral phonon emergence and their implications for phononic devices.

Findings

Higher dynamical stability in zigzag-stripe crystals

Emergence of chiral phonons with finite magnetizations and Berry curvatures

Potential for realizing phonon Hall effect in these systems

Abstract

We theoretically studied the phonon properties of the triangular-, stripe- and honeycomb-type electronic crystals recently found in two-dimensional semiconductor moir\'e patterns. By analyzing the phonon dispersions, we found the interaction induced lattice deformation in the zigzag-stripe crystal results in a much higher dynamical stability than in the linear-stripe crystal. Moreover, chiral phonons with finite magnetizations and large Berry curvatures can emerge in triangular and honeycomb crystals under time-reversal or inversion symmetry breaking. The small effective mass of the electrons allows the selective and efficient generation of chiral phonons from the optical activity of zone-center phonons combined with the anharmonicity, facilitating the realization of the phonon Hall effect. These findings point to an exciting new platform for exploring chiral phonons and the related topological phononic devices.