Determination of interatomic coupling between two-dimensional crystals –

using angle-resolved photoemission spectroscopy. Following the isolation of graphene, many other atomically thin two-dimensional crystals have been produced and can even be stacked on top of each other in a desired order to form so called van der Waals heterostructures.

Subtle changes in the stacking, especially the angle between the crystallographic axes of two adjacent layers, can have big impact on the properties of the whole heterostructure. We use angle-resolved photoemission spectroscopy measurements carried out at the Spectromicroscopy beamline at Elettra to obtain interatomic coupling for carbon atoms by studying a three-layer stack of graphene. The coupling between atoms in two two-dimensional crystals, knowledge of which is necessary to describe the properties of the stack, can be determined by studying a structure made of three layers with two similar interfaces but one with crystallographic axes aligned and one twisted. This is because each of the interfaces provides complementary information and together they enable self-consistent determination of the coupling.

Read more on the Elettra website

Image: Angle resolved photoemission spectrum revealing the electronic bands of a microscopic three layer device having aligned and twisted graphene-graphene interfaces. Measurable band gaps are used to self-consistently determine fundamental parameters of interatomic coupling.