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See detailPhonon-limited carrier mobility and resistivity from carbon nanotubes to graphene
Li, Jing; Pereira Coutada Miranda, Henrique UL; Niquet, Yann-Michel et al

in Physical Review. B: Condensed Matter and Materials Physics (2015)

Under which conditions do the electrical transport properties of one-dimensional (1D) carbon nanotubes (CNTs) and 2D graphene become equivalent? We have performed atomistic calculations of the phonon ... [more ▼]

Under which conditions do the electrical transport properties of one-dimensional (1D) carbon nanotubes (CNTs) and 2D graphene become equivalent? We have performed atomistic calculations of the phonon-limited electrical mobility in graphene and in a wide range of CNTs of different types to address this issue. The theoretical study is based on a tight-binding method and a force-constant model from which all possible electron-phonon couplings are computed. The electrical resistivity of graphene is found in very good agreement with experiments performed at high carrier density. A common methodology is applied to study the transition from one to two dimensions by considering CNTs with diameter up to 16 nm. It is found that the mobility in CNTs of increasing diameter converges to the same value, i.e., the mobility in graphene. This convergence is much faster at high temperature and high carrier density. For small-diameter CNTs, the mobility depends strongly on chirality, diameter, and the existence of a band gap. [less ▲]

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See detailTopological states in multi-orbital ​HgTe honeycomb lattices
Beugeling, Wouter; Kalesaki, Efterpi UL; Delerue, Christophe et al

in Nature Communications (2015), 6(6316),

Research on graphene has revealed remarkable phenomena arising in the honeycomb lattice. However, the quantum spin Hall effect predicted at the K point could not be observed in graphene and other ... [more ▼]

Research on graphene has revealed remarkable phenomena arising in the honeycomb lattice. However, the quantum spin Hall effect predicted at the K point could not be observed in graphene and other honeycomb structures of light elements due to an insufficiently strong spin–orbit coupling. Here we show theoretically that 2D honeycomb lattices of ​HgTe can combine the effects of the honeycomb geometry and strong spin–orbit coupling. The conduction bands, experimentally accessible via doping, can be described by a tight-binding lattice model as in graphene, but including multi-orbital degrees of freedom and spin–orbit coupling. This results in very large topological gaps (up to 35 meV) and a flattened band detached from the others. Owing to this flat band and the sizable Coulomb interaction, honeycomb structures of ​HgTe constitute a promising platform for the observation of a fractional Chern insulator or a fractional quantum spin Hall phase. [less ▲]

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See detailTopological States in Multi-Orbital Honeycomb Lattices of HgTe (CdTe) Quantum Dots
Beugeling, Wouter; Kalesaki, Efterpi UL; Delerue, Christophe et al

in ECS Transactions (2015), 69(5), 81-88

We summarize recent theoretical works on artificial graphene realized by honeycomb lattices of semiconductor (CdSe, HgTe, CdTe) quantum dots forming a two-dimensional single-crystalline sheet. In the case ... [more ▼]

We summarize recent theoretical works on artificial graphene realized by honeycomb lattices of semiconductor (CdSe, HgTe, CdTe) quantum dots forming a two-dimensional single-crystalline sheet. In the case of CdSe, we predict conduction bands with Dirac cones at two distinct energies and nontrivial flat bands. An analogous behavior is found in HgTe but, in addition, the strong spin-orbit coupling opens large topologically nontrivial gaps, leaving a flattened band detached from the others. We deduce that honeycomb lattices of HgTe quantum dots may constitute promising platforms for the observation of a fractional Chern insulator or a fractional quantum spin Hall phase. Similar predictions are made for CdTe but with smaller nontrivial gaps. [less ▲]

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