Emergent cavity junction around metal-on-graphene contacts

TL;DR

This paper uncovers how metal contacts induce a radial n-doped cavity in graphene, leading to unique transport signatures and emergent Landau levels, advancing understanding of metal-graphene interfaces.

Contribution

It reveals the microscopic origin of contact-induced cavities and their effects on graphene's electronic properties using simulations and experiments.

Findings

Contact induces a radial n-doped cavity around metal contacts.

Cavity causes secondary resistance peaks that decrease with contact size.

Emergent Landau levels form around the contact, demonstrating bulk-boundary correspondence.

Abstract

Harnessing graphene devices for applications relies on a comprehensive understanding of how to interact with them. Specifically, scattering processes at the interface with metallic contacts can induce reproducible abnormalities in measurements. Here, we report on emergent transport signatures appearing when contacting sub-micrometer high-quality metallic top contacts to graphene. Using electrostatic simulations and first-principle calculations, we reveal their origin: the contact induces an n-doped radial cavity around it, which is cooperatively defined by the metal-induced electrostatic potential and Klein tunneling. This intricate mechanism leads to secondary resistance peaks as a function of graphene doping that decreases with increasing contact size. Interestingly, in the presence of a perpendicular magnetic field, the cavity spawns a distinct set of Landau levels that interferes with the Landau fan emanating from the graphene bulk. Essentially, an emergent 'second bulk' forms around the contact, as a result of the interplay between the magnetic field and the contact-induced electrostatic potential. The interplay between the intrinsic and emergent bulks leads to direct observation of bulk-boundary correspondence in our experiments. Our work unveils the microscopic mechanisms manifesting at metal-graphene interfaces, opening new avenues for understanding and devising graphene-based electronic devices.