Philippe Dollfus, Viet Hung Nguyen and Jérôme Saint-Martin
Li Su, Youguang Zhang, Jacques-Olivier Klein, Yue Zhang , Arnaud Bournel, Albert Fert & Weisheng Zhao
Scientific Reports 5, Article number: 14905 (2015) doi:10.1038/srep14905
Présents : Arnaud, Philippe, Rania, Mai Chung, Hung, Damien, Jérôme Saint-Martin, Su Li, Adrien, Truong, Duy (new intern student from USTH).
Duy is working on III-V MOSFET, following Florian’s intern. Huy Viet is expected very soon…
Damien is back from Australia, Philippe from Sicilia.
Flagship graphene NanoSaclay in progress. Discussion with ICMMO, LPS, CEA LEM on very well controlled nanomesh and QD. Merging with Talal Mallah project? Others? In parallel, flagship spintronics NanoSaclay…
Flagship graphene EU : phase 1 (scientific aspects) on graphene materials for spintronics OK, with LPS (Hélène Bouchiat), Ec. Polytechnique, ICMMO. While we were quite pessimistic. Next?? Political selection…
Call « attractivité 2015 » Univ. Paris-Sud for young researchers and their new activities→ July 11, 2014, cf. Michele.
Jérôme L (now in Doctoriales) has submitted a paper to « Nanoscale and microscale heat transfer IV », Oct. 1517 Lyon.
Annual meeting of the GDRI Graphene, Strasbourg, France, September 21-25. Abstracts due July 1st. Philippe will be in USA during this period.
Call of papers on transistors with steep subthreshold swing for low-poweer electronics, from IEEE Jiurnal of electron devices. Truong? Not interesting…
Revised JAP from Trang about self heating due to Wednesday June 18.
Monday, June 30 at 14h30, Hung…
Monday July 7 at 14h30 but who???
Picnic on July 4. Where???
Summer school on graphene in Cargèse! Organized by Annick Loiseau, Claire Berger, Didier Mayou and…
A lecture from Mildred S. Dresselhaus(MIT): stories of carbon material.
One from Didier Mayou (Grenoble) on electrical properties of graphene.
Many body effect by a guy from Berkeley, on GW theory and superlattices.
Quantum effects : Mark Oliver Goerbig (UPSud) on quantum Hall effect. Stephan Roche on Klein tunneling, symmetry-breaking effects… And his book!
Disorder effetcs by Hélène Bouchait (impurety scattering) and François Ducastelle (defect and doping).
Optoelectronics ad power conversion by a guy from Barcelona (ICFO).
Also experimental aspects: Raman spectroscopy, TEM, STM/STS, synthesis (CVD, modeling by Christophe Bichara from Marseille), hybrid structures, liquid form of CNT and graphene, applications (Richard Martel on FETs, Pierre Seneor on spintronics → STTMRAM, Alberto Bianco from Strasbourg on biomedical applications).
No CD, no hardcopy of slides! But information on a website, see Mai Chung.
Présents : Michele Amato, Salim Berrada, Arnaud Bournel, Philippe Dollfus, Jérôme Larroque, Mai Chung Nguyen, Jérôme Saint Martin, Su Li, Tran Van Truong, Adrien Vincent.
Salim and Philippe with Plaçais group about Klein transistor nearly accepted (IOP 2D mat).
Monastir paper with Arnaud about optical effects in GeSn quantum wells accepted for JAP: « Wave-function engineering and absorption spectra in Si0.16Ge0.84/Ge0.94Sn0.06/Si0.16Ge0.84 strained on relaxed Si0.10Ge0.90 type I quantum well ». But not very original in comparison of a previous paper on Ge wells. Naima as 1st author.
ISCAS of Adrien accepted! In Australia in June.
Next deadlines: tomorrow for E-MRS -> Michele has already submitted, Jérôme L. should write an abstract too. In Lille May 19-24.
Summer school Graphene 2014 -> Truong and Mai Chung (?). Deadline for the conference Graphene (Toulouse) = 1/2 -> Trung, Mai Chung.
IWCE, deadline 28/1. Same day as Comics lunch!
Ulis, February 3 but…
Next Comics meetings
On Monday afternoon. About 1 per month.
A (very) short introduction to Density Functional Theory, by Michele
-> For atomic structure, thermodyn, chemical, electronic and scattering properties.
Nobel prize for DFT in chemistry. 1998: Walter Kohn and John Pople.
Semi-empirical methods (Hückel, based on Hartree-Fock formalism) -> good for large systems. Can fail if the computed molecule is not close to the database of parametrized molecules.
DFT -> very good scalability.
Many body problem -> Ne electrons, Nn nuclei, Schrödinger equation to solve… With kinetic energies and potential: repulsion between nuclei, between electrons and between electrons and nuclei. How to deal with 1023 particles?
Born-Oppenheimer separation -> nuclei frozen in their equilibrium positions. But wavefunctions remain very complex! And experimentally measurable. While electron density is observable, e.g.by X-rays.
Hohenberg-Kohn theorem I: the relation between the potential and the electron density is invertible. Then, the ground state expectation value of any observable depends only on the electron density.
Hohenberg-Kohn theorem II: the total energy functional has a minimum, the ground state energy E0, in correspondence to the ground state density r0 -> proof of the existence of the universal functional without determining it.
Kohn-Sham scheme -> r0 can be calculated thanks to an artificial system of non-interacting particles. Using one-particle orbitals which are not real wavefunctions. And Kohn-Sham potential = vion(r) + vH(r) + vxc(r) where vH describes the classic electrostatic potential and vxc is the exchange-correlation potential, for taking into account the effect of interactions between particles.
Approximation for vxc -> local description.
Self consistent flow diagram to solve the Kohn-Sham scheme, as a function of the density.
De-freezing the nuclei… Cf. Feynman, Phys Rev 56 (4), 340 (1939) “Forces in molecules” (http://dx.doi.org/10.1103/PhysRev.56.340) -> Hellmann-Feynman theorem for an analytical solution. Wikipedia: proven independently by many authors, including Paul Güttinger (1932), Wolfgang Pauli (1933), Hans Hellmann (1937) and Richard Feynman (1939). This does not correspond to phonon problem!
For further development :
- September 18th, thursday at 10h in the meeting room (119).
- October 23th, thursday at 10h in the meeting room (119) : Jérôme L.
- November 20th, thursday at 10h in the meeting room (119) : Adrien
- December 18th, thursday at 10h in the meeting room (119) : Truong
- February 2d,monday at 10h30 in the meeting room (119) : Li
* News : Hung is back ! New thesis proposal about Ge nanowires
* Presentation by Mai chung on strained graphene
* Enhanced thermoelec efficiency in vertical graphene junctions, Viet Hung Nguyen