Observation of the Spin-Orbit Gap in Bilayer Graphene by One-Dimensional Ballistic Transport
Luca Banszerus, Benedikt Frohn, Thomas Fabian, Sowmya Somanchi, Alexander Epping, M. Müller, Daniel Neumaier, Kenji Watanabe, Takashi Taniguchi, Florian Libisch, Bernd Beschoten, Fabian Hassler, Christoph Stampfer
Abstract
We report on measurements of quantized conductance in gate-defined quantum point contacts in bilayer graphene that allow the observation of subband splittings due to spin-orbit coupling. The size of this splitting can be tuned from 40 to 80 μeV by the displacement field. We assign this gate-tunable subband splitting to a gap induced by spin-orbit coupling of Kane-Mele type, enhanced by proximity effects due to the substrate. We show that this spin-orbit coupling gives rise to a complex pattern in low perpendicular magnetic fields, increasing the Zeeman splitting in one valley and suppressing it in the other one. In addition, we observe a spin polarized channel of 6e^{2}/h at high in-plane magnetic field and signatures of interaction effects at the crossings of spin-split subbands of opposite spins at finite magnetic field.