Ghost anti-crossings caused by interlayer umklapp hybridization of bands in 2D heterostructures

TL;DR

This paper demonstrates that interlayer umklapp processes in 2D heterostructures can cause ghost anti-crossings in electronic bands, offering a new method for twist-controlled band structure engineering.

Contribution

It provides experimental evidence of interlayer umklapp hybridization causing ghost anti-crossings, a novel phenomenon in 2D heterostructures.

Findings

Interlayer umklapp processes cause hybridization in 2D heterostructures.

Ghost anti-crossings observed in graphene/InSe heterostructures.

Potential for twist-controlled electronic band engineering.

Abstract

In two-dimensional heterostructures, crystalline atomic layers with differing lattice parameters can stack directly one on another. The resultant close proximity of atomic lattices with differing periodicity can lead to new phenomena. For umklapp processes, this opens the possibility for interlayer umklapp scattering, where interactions are mediated by the transfer of momenta to or from the lattice in the neighbouring layer. Using angle-resolved photoemission spectroscopy to study a graphene on InSe heterostructure, we present evidence that interlayer umklapp processes can cause hybridization between bands from neighbouring layers in regions of the Brillouin zone where bands from only one layer are expected, despite no evidence for moir/'e-induced replica bands. This phenomenon manifests itself as 'ghost' anti-crossings in the InSe electronic dispersion. Applied to a range of suitable 2DM pairs, this phenomenon of interlayer umklapp hybridization can be used to create strong mixing of their electronic states, giving a new tool for twist-controlled band structure engineering.