High density carriers at a strongly coupled graphene-topological insulator interface

TL;DR

This study investigates a strongly coupled graphene-topological insulator interface, revealing unique interface carriers with large Fermi surfaces through quantum oscillations, suggesting novel charge transfer or mini-band effects.

Contribution

It demonstrates the existence of high-density, interface-specific carriers in a strongly coupled graphene-topological insulator device, highlighting new physical phenomena at the interface.

Findings

Quantum oscillations indicate well-resolved Landau levels.

Presence of large Fermi surface hole carriers at the interface.

Interface carriers likely due to charge transfer or mini-band transport.

Abstract

We report on a strongly coupled bilayer graphene (BLG) - \bise\ device with a junction resistance of less than 1.5 k$\Omega\mu$m$^2$. This device exhibits unique behavior at the interface, which cannot be attributed to either material in absence of the other. We observe quantum oscillations in the magnetoresistance of the junction, indicating the presence of well-resolved Landau levels due to hole carriers of unknown origin with a very large Fermi surface. These carriers, found only at the interface, could conceivably arise due to significant hole doping of the bilayer graphene with charge transfer on the order of 2$\times$10$^{13}$ cm$^{-2}$, or due to twist angle dependent mini-band transport.