Trivial and inverted Dirac bands and the emergence of quantum spin Hall states in graphene on transition-metal dichalcogenides Article Swipe
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· 2016
· Open Access
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· DOI: https://doi.org/10.1103/physrevb.93.155104
· OA: W2198265245
Proximity orbital and spin-orbital effects of graphene on monolayer\ntransition-metal dichalcogenides (TMDCs) are investigated from\nfirst-principles. The Dirac band structure of graphene is found to lie within\nthe semiconducting gap of TMDCs for sulfides and selenides, while it merges\nwith the valence band for tellurides. In the former case the proximity-induced\nstaggered potential gaps and spin-orbit couplings (all on the meV scale) of the\nDirac electrons are established by fitting to a phenomenological effective\nHamiltonian. While graphene on MoS$_2$, MoSe$_2$, and WS$_2$ has a\ntopologically trivial band structure, graphene on WSe$_2$ exhibits inverted\nbands. Using a realistic tight-binding model we find topologically protected\nhelical edge states for graphene zigzag nanoribbons on WSe$_2$, demonstrating\nthe quantum spin Hall effect. This model also features "half-topological\nstates", which are protected against time-reversal disorder on one edge only.\n
