Tuning anti-Klein to Klein tunneling in bilayer graphene

Renjun Du, Ming-Hao Liu, Jens Mohrmann, Fan Wu, Ralph Krupke, Hilbert v. Löhneysen, Klaus Richter, Romain Danneau

Published 2017-03-21Version 1

We report that in gapped bilayer graphene, quasiparticle tunneling and the corresponding Berry phase exhibit features of single layer graphene. The Berry phase is detected by a high-quality Fabry-P\'{e}rot interferometer based on bilayer graphene. We found that the Berry phase is continuously tuned from $2\pi$ to $0.34\pi$ in gapped bilayer graphene by raising the Fermi energy of charge carriers, in contrast to the Berry phase of $2\pi$ in pristine bilayer graphene. Particularly, a Berry phase of $\pi$, which is the standard value for single layer graphene, is also observed in gapped bilayer graphene. By analyzing the transmission probability of charge carriers at normal incidence, we demonstrate a transition from (nearly perfect) Klein tunneling, a typical phenomenon in single layer graphene, to broken anti-Klein tunneling, known in gapped bilayer graphene, by decreasing the Berry phase. The maximum transmission probability of 0.87, which is close to unity, indicates that complete Klein tunneling is achievable in gapped bilayer graphene.