G. Tkachov, Martina Hentschel
Band gap engineering in graphene may open the routes towards transistor devices in which electric current can be switched off and on at will. Is, however, a semiconducting band gap alone sufficient to quench the current in graphene? In this paper we demonstrate that despite a bulk band gap graphene can still have metallic conductance along the sample edges. We find this for single-layer graphene with a zigzag-type boundary which hosts gapless propagating edge states even in the presence of a bulk band gap. By generating inter-valley scattering, sample disorder reduces the edge conductance. However, for weak scattering a metallic regime emerges with the diffusive conductance G = (e^2/h)(l_KK'/ L) per spin, where l_KK' is the transport mean-free path due to the inter-valley scattering and L >> l_KK' is the edge length. We also take intra-valley scattering by smooth disorder (e.g. by remote ionized impurities in the substrate) into account. Albeit contributing to the elastic quasiparticle life-time, the intra-valley scattering has no effect on G.
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http://arxiv.org/abs/1208.1951
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