Fig. 1
From: Topological valley transport at the curved boundary of a folded bilayer graphene
Valleytronic device based on a folded bilayer graphene. a Components of the folded bilayer graphene (folded-BLG) valleytronic device. The folded-BLG is sandwiched by hexagonal boron nitride (hBN) crystals that separate the material from the metallic gates. Under a transverse electric field, the bulk behaves likely semiconductor with band gap and a topological 1D conducting channel forms at the curved boundary, where the valley-index defines the direction of propagation. b Optical image of a folded-BLG transferred on top of the bottom hBN flake. Dashed lines indicate the position of the electric terminals. Scale bar: 4 μm. c A false-color atomic force microscopy (AFM) image of device 1 before the transference of the top hBN. The AFM measurement reveals that the curved boundary is free from contamination of fabrication processes. Scale bar: 1 μm. d Electrostatic potential energy (Δ/2) of the bilayer graphene (BLG) layers, calculated relative to the center of each BLG. The layer energies reverse sign from the bottom BLG to the top BLG and vanish across the curved boundary, where the electric field is parallel to the layers. This variation of the electrostatic potential energy enables the formation of a domain wall at the curved boundary. e Illustration of the pair of kink states localized at inequivalent points K and K’ in the Brillouin zone of BLG, having opposite group-velocities for different valleys. In the domain wall, these edge states propagate in opposite one-dimensional directions due their chiral nature
