Title: Bilayer graphene: band gap, mass and valley Hall edge states

 

Abstract:

  Valley and layer degrees of freedom are distinguish characteristics of atomically thin two-dimensional crystals with hexagonal symmetry, the control of which can lead to valley Hall effect and a variety of emergent ground states manifesting in the quantum Hall regime and perhaps also novel concepts of nanoelectronics. Bernal stacked Bilayer graphene is a terrific material to explore these phenomena. In this talk, I will discuss our experimental work on probing the band structure, electron-hole asymmetry  effective mass and electric-field induced band gap in bilayer graphene. I will also show how we overcome sample quality and lithographic challenges to build split dual-gated devices, where the abrupt reversal of the valley Hall index at the line junction of two oppositely electrically biased bilayer graphene gives rise to one-dimensional edge states. I will present the experimental evidences of such edge states and discuss its backscattering mechanisms. In a moderate magnetic field, the resistance of the four-fold degenerate edge states is close to the ballistic limit of h/4e^2.