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Abstract : From semiconductor nanocrystals to artificial graphene and topological insulators

E. Kalesaki1,2, C. Delerue1, C. Morais Smith3, W. Beugeling3,4, G. Allan1, D. Vanmaekelbergh5
1 IEMN – Département ISEN, UMR CNRS 8520, 59046 Lille, France
2 Physics and Materials Science Research Unit, University of Luxembourg, 162a avenue de la Faïencerie L-1511
Luxembourg, Luxembourg
3 Institute for Theoretical Physics, University of Utrecht, 3584 CE Utrecht, Netherlands
4 Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße 38, 01187 Dresden, Germany.
5 Debye Institute for Nanomaterials Science, University of Utrecht, 3584 CC Utrecht, Netherlands

Recent advancements in colloidal chemistry indicate that two-dimensional single-crystalline sheets of semiconductors forming a honeycomb lattice can be synthesized from semiconductor nanocrystals [1,2]. We have performed atomistic tight-binding calculations of the band structure of CdSe sheets with such a nano-geometry [3,4]. We predict in the conduction band Dirac cones at two distinct energies and nontrivial flat bands and, in the valence band, topological edge states. These edge states are present in several electronic gaps opened in the valence band by the spin-orbit coupling and the quantum confinement in the honeycomb geometry. The origin of the non-trivial topology is revealed [4]. The lowest Dirac conduction band has s-orbital character and is equivalent to the  bands of graphene but with renormalized couplings. The conduction bands higher in energy have no counterpart in graphene ; they combine a Dirac cone and flat bands because of their porbital character. These systems emerge as remarkable platforms for studying complex electronic phases starting from conventional semiconductors.

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S. Bals, and D. Vanmaekelbergh, Science 344, 1377-1380 (2014).
[3] E. Kalesaki, C. Delerue, C. Morais Smith, W. Beugeling, G. Allan, D. Vanmaekelbergh, Phys. Rev. X 4,
011010 (2014).
[4] C. Delerue, Phys. Chem. Chem. Phys., 2014, DOI : 10.1039/C4CP01878H