Electrostatically-defined graphene nanoribbon

Electron confinement of Dirac fermions in graphene has remained a longstanding challenge.~ Owing to the gapless nature of the bandstructure, conventional depletion-gate schemes cannot be employed. Nano scale constrictions may be realized by etching, however this results in significant edge disorder, that tends to dominate the resulting device characteristics. ~ Here, we discuss a new approach to electrostatic confinement in graphene where we take advantage of either a Moiré induced energy gap (present when graphene is fabricated with zero-angle alignment to BN) as well as the $\nu =$ 0 quantum Hall state (a magnetic field induced energy gap without edge states). We use a dual-gated structure to set one region to the induced gap, while the other varies the Fermi energy in the confinement region.~ One dimensional nanoribbons are realized by utilizing carbon nanotubes as one of the electrostatic gates, demonstrated by the appearance of quantized step sin conductance.~