Magic-angle Bilayer Phononic Graphene

TL;DR

This paper introduces twisted bilayer phononic graphene, demonstrating the existence of magic angles with ultra-flat bands, offering a new, accessible platform for studying twistronics and potential applications in acoustic sensing.

Contribution

It extends twistronics to acoustics by establishing the first phononic analog of twisted bilayer graphene with tunable magic angles and flat bands.

Findings

Discovery of magic angles in bilayer phononic graphene

Ultra-flat bands observed at specific twist angles

Enhanced control over interlayer coupling in phononic systems

Abstract

Thanks to the recent discovery on the magic-angle bilayer graphene, twistronics is quickly becom11 ing a burgeoning field in condensed matter physics. This letter expands the realm of twistronics to acoustics by introducing twisted bilayer phononic graphene, which remarkably also harbors the magic angle, evidenced by the associated ultra-flat bands. Beyond mimicking quantum mechanical behaviors of twisted bilayer graphene, we show that their acoustic counterpart offers a considerably more straightforward and robust way to alter the interlayer hopping strength, enabling us to unlock magic angles (> 3 degrees) inaccessible in classical twisted bilayer graphene. This study, not only establishes the acoustical analog of twisted (magic-angle) bilayer graphene, providing a testbed more easily accessible to probe the interaction and misalignment between stacked 2D materials, but also points out the direction to a new phononic crystal design paradigm that could benefit applications such as enhanced acoustic emission and sensing.