Stabilizing sample-wide Kekul\'e orders in graphene/transition metal dichalcogenide heterostructures

TL;DR

This paper demonstrates that using transition metal dichalcogenides as substrates can stabilize large-area, sample-wide Kekule9 lattice distortions in graphene, revealing new electronic phases and substrate-sensitive properties.

Contribution

The study introduces a method to stabilize and observe robust, sample-wide Kekule9 orders in graphene via heterostructures with TMDs, a significant advancement over previous approaches.

Findings

Kekule9 distortions are stabilized across entire graphene/TMD heterostructures.

Three distinct Kekule9 bond textures are directly imaged.

Substrate choice influences the electronic properties of graphene.

Abstract

Kekul\'e phases are Peierls-like lattice distortions in graphene that are predicted to host novel electronic states beyond graphene (1-8). Although the Kekul\'e phases are realized in graphene through introducing electron-electron interactions at high magnetic fields (9-11) or adatom superlattices (12-15), it is still an extremely challenge to obtain large-area graphene Kekul\'e phases in experiment. Here we demonstrate that sample-wide Kekul\'e distortions in graphene can be stabilized by using transition metal dichalcogenides (TMDs) as substrates and the induced Kekul\'e orders are quite robust in the whole graphene/TMDs heterostructures with different twist angles. The commensurate structures of the heterostructures provide periodic scattering centers that break the translational symmetry of graphene and couple electrons of the two valleys in graphene, which tips the graphene toward global Kekul\'e density wave phases. Unexpectedly, three distinct Kekul\'e bond textures stabilized at various energies are directly imaged in every graphene/TMDs heterostructure. Our results reveal an unexpected sensitivity of electronic properties in graphene to the supporting substrates and provide an attractive route toward designing novel phases in graphene/TMDs heterostructures.