Topic: Colloidal semiconductor nanocrystals: From single objects to artificial solids
Speaker: Professor Chrisophe Delerue - University of Lille, France
Host: Professor Ben Levine
Date: Thursday, December 6, 2018
Time: 12:00 PM
Location: 1400 BPS
Daniel Vanmaekelbergh1, Christophe Delerue2
1Debye Institute, Utrecht University, The Netherland
2IEMN – UMR 8520 – Villeneuve d'Ascq, France
Semiconductor nanocrystals prepared by colloidal chemistry have been studied for more than three decades but it is only now that they are employed in mass-market commercial applications. Nowadays, these nano-objects can be fabricated with an excellent control of their composition, size and shape in such manner that their electronic structure and their optical properties can be accurately tuned. Semiconductor nanocrystals can be sometimes considered as artificial atoms for reasons which will be discussed. In this talk, I will present recent advances in the field that potentially open new perspectives of application. I will show that the artificial atoms can be self-assembled to form new types of two-dimensional crystals in which the electronic structure results from the effect of the periodic scattering of the electrons induced by the nanogeometry. Recent progress in colloidal chemistry enables the fabrication of materials in which each nanocrystal can be considered as a LEGO brick®. Moreover this concept of LEGO® can be extended to the calculation of the electronic band structure of the superlattices. By combining the original band structure of the bulk semiconductor and the effects of the nano-structuring, we show that these new materials are characterized by exotic band structures including Dirac cones, non-trivial flat band bands, and topological bands.
 Colloidal nanocrystals as LEGO® bricks for building electronic band structure models, Athmane Tadjine, Christophe Delerue, Physical Chemistry Chemical Physics 2018 | DOI: 10.1039/C7CP08400E.
 Transport Properties of a Two-Dimensional PbSe Square Superstructure in an Electrolyte-Gated Transistor, M. Alimoradi Jazi, V. A. E. C. Janssen, W. H. Evers, A. Tadjine, C. Delerue, L. D. A. Siebbeles, H. S. J. van der Zant, A. J. Houtepen, D. Vanmaekelbergh, Nano Letters 2017 | DOI: 10.1021/acs.nanolett.7b01348.
 From lattice Hamiltonians to tunable band structures by lithographic design, A. Tadjine, G. Allan, C. Delerue, Phys. Rev. B 94, 7 (2016) 075441 | doi: 10.1103/PhysRevB.94.075441.
 Topological states in multi-orbital HgTe honeycomb lattices, W. Beugeling et al., Nat. Commun. 6 (2015) 6316 | doi: 10.1038/ncomms7316.
 Dirac cones, topological edge states, and nontrivial flat bands in two-dimensional semiconductors with a honeycomb nanogeometry, E. Kalesaki et al, Phys. Rev. X 4, 1 (2014) 011010 | doi: 10.1103/PhysRevX.4.011010.