title: Two-dimensional topological insulator state and topological phase transition in bilayer graphene.
abstract: We show that gated bilayer graphene hosts a strong topological insulator (TI) phase in the presence of Rashba spin-orbit (SO) coupling. We find that gated bilayer graphene under preserved time-reversal symmetry is a quantum valley Hall insulator for small Rashba SO coupling λ(R), and transitions to a strong TI when λ(R)>√[U(2)+t(⊥)(2)], where U and t(⊥) are, respectively, the interlayer potential and tunneling energy. Different from a conventional quantum spin Hall state, the edge modes of our strong TI phase exhibit both spin and valley filtering, and thus share the properties of both quantum spin Hall and quantum valley Hall insulators. The strong TI phase remains robust in the presence of weak graphene intrinsic SO coupling.
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA. zhqiao@physics.utexas.edu
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Qiao
authors.forename: Wang-Kong
authors.initials: WK
authors.lastname: Tse
authors.forename: Hua
authors.initials: H
authors.lastname: Jiang
authors.forename: Yugui
authors.initials: Y
authors.lastname: Yao
authors.forename: Qian
authors.initials: Q
authors.lastname: Niu