Xiao Li, Zhenhua Qiao, Jeil Jung, Qian Niu
Gapless edge modes hosted by gated ABC trilayer graphene display unique features when a bulk gap is opened due to inversion symmetry breaking. We show that trilayer graphene with half-integer valley Hall conductivity leads to spatially asymmetric valley-resolved edge mode pairs, resulting in a net valley polarized current. This unusual characteristic is preserved in the presence of Rashba spin-orbit coupling that eventually turns an unbalanced ABC trilayer into a ${Z}_2$ strong topological insulator, i.e. there are \emph{unequal} odd numbers of spin and valley helical edge mode pairs flowing along opposite zigzag ribbon boundaries.
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http://arxiv.org/abs/1203.4033
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