Miniband Generation by Surface Acoustic Waves

TL;DR

This paper presents a method to create tunable, externally controllable superlattices on 2D materials using surface acoustic waves, enabling dynamic control over their electronic band structures.

Contribution

It introduces a novel acoustoelectric superlattice technique that allows in-situ tuning of band structures in 2D materials via surface acoustic wave parameters.

Findings

Tunable superlattice periodicity between moiré and optical lattice scales.

External control of superlattice amplitude through acoustic wave power.

Generation of flat bands with nontrivial valley Chern numbers.

Abstract

We introduce a new class of tunable periodic structures, formed by launching two obliquely propagating surface acoustic waves on a piezoelectric substrate that supports a two-dimensional quantum material. The resulting acoustoelectric superlattice exhibits two salient features. First, its periodicity is widely tunable, spanning a length scale intermediate between moir\'e superlattices and optical lattices, enabling the formation of narrow, topologically nontrivial energy bands. Second, unlike moir\'e systems, where the superlattice amplitude is set by intrinsic interlayer tunneling and lattice relaxation, the amplitude of the acoustoelectric potential is externally tunable via the surface acoustic wave power. Using massive monolayer graphene as an example, we demonstrate that varying the frequencies and power of the surface acoustic waves enables in-situ control over the band structure of the 2D material, generating flat bands and nontrivial valley Chern numbers, featuring a highly localized Berry curvature.