Sylvain Lecler (ICube)
Séminaire d’information sur l’Institut Photonique Grand Est : il s’agit d’une fédération entre plusieurs laboratoires du Grand Est, et un petit nombre d’entreprises actifs dans le secteur de la photonique.Les universités de Lorraine, Mulhouse, Strasbourg, l’UTT Troyes et Centrale Supelec ont signé l’accord de consortium.
Le but principal de la fédération est de promouvoir la photonique comme un axe scientifique et technologique majeure au niveau de la région, au même titre que les matériaux, l’environnement ou le bio-médicale. C’est un point important au moment des AAP de la région pour les co-financements de thèse ou de post-doc, D’autres opportunités sont les financements de projet par le FEDER.
Le directeur de l’Institut et Marc Sciamanna (Centrale Supelec, Metz). Hervé Rinner (ISL, Nancy) et Sylvain sont les co-directeurs.
Venez profiter de ce séminaire pour vous mettre au courant de cette nouvelle fédération régionale.
Paul EYMÉOUD (Research Scientist at SiClade Technologies)
Lien de connexion par bbb unistra, le 12 mars 2024 à partir de 14h50 :
https://bbb.unistra.fr/b/alo-pwp-ctx-flx
Benjamin BACQ-LABREUIL (Institut Quantique de l’Université de Sherbrooke – Canada)
Abstract : High-temperature n-layer cuprate superconductors have the remarkable universal feature that the maximum transition temperature Tc is always obtained for the tri-layer compound. It remains unclear how the recent breakthroughs, highlighting the relation of the charge transfer gap (CTG) and the spin exchange J with the pairing density, can be related to this universality. By integrating an exact diagonalization solver to a density functional theory (DFT) plus cluster dynamical mean-field theory (CDMFT) framework, we were able to carry charge self-consistent DFT+CDMFT calculations for n =1-5 multilayer cuprates. Remarkably, the undoped compounds already host a peculiar behavior as a function of n: the CTG first decreases until reaching a minimum at n=3, and then stabilizes. The CTG is smaller in the inner CuO2 planes, and consequently the spin exchange J is larger as compared to the outer planes, which corroborates the experimental evidence of stronger antiferromagnetic spin fluctuations in the inner planes. We trace back the miscroscopic origin of these observations to the existence of interstitial conduction states confined between the CuO2 layers which favor the inner planes. Our work paves the way towards ab initio material-specific predictions of the superconducting order parameter.
Contact : Mébarek ALOUANI : mebarek.alouani@ipcms.unistra.fr
Connexion links on March 5th, 2024 from 14h50 :
https://cnrs.zoom.us/j/94911816568?pwd=c0JoY2EyU1VJOG5SN2NsQXNDRG81Zz09
Meeting ID: 949 1181 6568
Secret code: 0FaFbn
Speaker: Mattia Udina, La Sapienza Roma
The abstract is available there.
Kevin Dedecker (Institut Européen des Membranes (IEM); CNRS, ENSCM, Univ Montpellier)
Abstrasct
Dr. Maurizio Mastropasqua Talamo (Laboratoire Moltech-Anjou, Université d’Angers)
Abstract :
Starting from initial purposes of molecular recognition, the study of chiral pi-conjugated molecules and supramolecular assemblies have led over time to a deeper understanding of chirality-related properties which do not only rely upon geometric pairing but also involve polarization in light-matter interaction and spin selectivity in charge transport. These new properties have boosted the interest in the development of chiral organic semiconductors for advanced optoelectronics applications.
Many asymmetric synthetic techniques which are particularly important in the field of pharmaceutical synthesis, can enable the practical modification of pi-conjugated scaffolds with various stereogenic motifs, resulting in molecular semiconductors and chromophores showcasing diverse chirality-related properties.
Some examples of asymmetric modification of molecular semiconductors and chromophores will be given in this lecture along with a discussion about chirality-related properties observed within the newly synthesized materials.
Dr. Laurence CROGUENNEC (Institut de Chimie de la Matière Condensée de Bordeaux)
Directrice de recherche CNRS, directrice adjointe de l’ICMCB
Abstract :
Known from all chemists for decades, the sodium-ion battery technology was dethroned in the 1980s by the lithium-ion battery that offered better performance. The major interest of sodium is to be a sustainable resource in comparison to lithium. The technology is thus back on the scene as an ecological, economical and reliable alternative to the lithium-ion battery. I will present the challenges of this research field, and highlight some of our results. I will show how we were able to (i) discover a new family of NASICON structural type materials NaxV2(PO4)3, and (ii) demonstrate how the chemistry of mixed anions and in particular the competition between the ionic bond V-F and the very covalent vanadyle-type bond V=O has an impact on the properties of Na3V2(PO4)2F3-yOy. I will demonstrate that only the in-depth control of the relationship synthesis/composition/atomic and electronic structure allows to tune the properties in the battery. I will illustrate also that monitoring in situ and operando, especially at large scale facilities, the synthesis of electrode materials and their evolution when used in batteries is essential. Changes in the composition and structure of the materials must be studied in their environment (in situ), and in real time (operando) during their preparation or operation of the battery because they are most often in conditions out of equilibrium. The experiments thus conducted allow to study the dynamics of reactions, essential for the understanding of the material and optimization of its performance in the electrochemical storage system.
Maria Chatzieleftheriou (CPHT, Ecole Polytechnique, Palaiseau)
Abstract : voir affiche jointe
Dr. Ludovic Favereau (ISCR, Université de Rennes)
Abstract
Sophie WEBER (ETH-Zurich, Department of Materials, Zurich, Switzerland)
Theoretical arguments [1,2] and experimental measurements [3-6] have definitively shown that antiferromagnets (AFMs) with particular bulk symmetries can possess a nonzero magnetic dipole moment per unit area or “surface magnetization” on certain surface facets. Such surface magnetization underlies intriguing physical phenomena like interfacial magnetic coupling, and can be used as a readout method of antiferromagnetic domains. However, a universal description and understanding of antiferromagnetic surface magnetization is lacking. I first introduce a classification system based on whether the surface magnetization is sensitive or robust to roughness, and on whether the magnetic dipoles at the surface of interest are compensated or uncompensated. I then show that every type of surface magnetization can be identified and understood in terms of bulk magnetic multipoles, which are already established as symmetry indicators for bulk magnetoelectric responses [7]. This intimate correspondence between antiferromagnetic surface magnetization and magnetoelectric responses at both linear and higher orders reveals that selection and control of the antiferromagnetic order parameter via magnetoelectric annealing may be possible in many more materials and surfaces than previously believed. I use density functional calculations to illustrate that nominally compensated (10-10) and (-12-10) surfaces in magnetoelectric Cr2O3 develop a finite magnetization density at the surface, in agreement with our predictions based on both group theory and the ordering of the bulk multipoles. Finally, I present magnetotransport results by collaborators confirming our ab-initio and theoretical predictions of finite magnetization on these surfaces. Our analysis [8,9] provides a comprehensive basis for understanding the surface magnetic properties and their intimate correspondence to bulk magnetoelectric effects in antiferromagnets, and may have important implications for technologically relevant phenomena such as exchange bias coupling.
[1] A. F. Andreev, JETP Lett. 63, 756 (1996)
[2] K. D. Belashchenko, Phys. Rev. Lett. 105, 147204 (2010)
[3] X. H et al, Nature Mat. 9, 579 (2010)
[4] N. Wu et al., Phys. Rev. Lett. 106, 087202 (2011)
[5] P. Appel et al., Nano Lett. 19, 1682 (2019)
[6] M. S. Wörnle et al., Phys. Rev. B 103, 094426 (2021)
[7] N. A. Spaldin et al., Phys. Rev. B 88, 094429 (2013)
[8] S. F. Weber et al., arXiv:2306.06631 (2023)
[9] O. V. Pylypovskyi, S. F. Weber et al., arXiv 2310.13438 (2023)
Contact : Mébarek ALOUANI : mebarek.alouani@ipcms.unistra.fr
