Tunneling in graphene-topological insulator hybrid devices

Graphene and topological insulators are both materials where electronic transport properties are dictated by relativistic energy-momentum dispersion relations. Several topological insulators, such as Bi₂Se₃, have a layered structure, with weak out-of-plane van-der-Waals bonds, allowing for easy exfoliation into thin flakes. In the talk I will describe how layered materials such as graphene and Bi₂Se₃ can be vertically stacked, creating a new kind of heterostructure. In electronic devices fabricated from such heterostructures, each material is contacted individually, and electronic properties of the interface are measured at low tempertures. The measurements reveal that the interface is a tunnel junction of exceptionally good quality. This tunnel junction can then be used to perform mutual inelastic spectrocsopy, revealing the phonon spectra of both materials, and to measure the density-dependent spectra of graphene and bilayer graphene.