Manipulating moires by controlling heterostrain in van der Waals devices

TL;DR

This paper demonstrates in-situ manipulation of moire superlattices in van der Waals devices through heterostrain control, enabling tunable electronic properties and expanded exploration of moire lattice phenomena.

Contribution

It introduces a sliding-based technique to apply uniaxial heterostrain exceeding 1%, allowing precise control over moire shape and size in vdW heterostructures.

Findings

Heterostrain distorts and enlarges moire patterns.

Transport measurements show shifted superlattice peaks.

Electronic structure calculations reveal reduced bandwidth and anisotropic Fermi surfaces.

Abstract

Van der Waals (vdW) moires offer tunable superlattices that can strongly manipulate electronic properties. We demonstrate the in-situ manipulation of moire superlattices via heterostrain control in a vdW device. By straining a graphene layer relative to its hexagonal boron nitride substrate, we modify the shape and size of the moire. Our sliding-based technique achieves uniaxial heterostrain values exceeding 1%, resulting in distorted moires that are larger than those achievable without strain. The stretched moire is evident in transport measurements, resulting in shifted superlattice resistance peaks and Landau fans consistent with an enlarged superlattice unit cell. Electronic structure calculations reveal how heterostrain shrinks and distorts the moire Brillouin zone, resulting in a reduced electronic bandwidth as well as the appearance of highly anisotropic and quasi-1-dimensional Fermi surfaces. Our heterostrain control approach opens a wide parameter space of moire lattices to explore beyond what is possible by twist angle control alone.