Soutenance de thèse : Satakshi Pandey

Satakshi Pandey (IPCMS / DMONS)

La soutenance aura lieu Vendredi 18 octobre à 9h30 à l’auditorium de l’IPCMS

Ce travail a été réalisé sous la direction du Dr Jean François Dayen et du Dr David Halley (DMONS).

Mini-workshop Franco-Indien sur les matériaux et dispositifs ferroïques bi-dimensionnels

Ce workshop est organisé avec le soutien du CEFIPRA, des Ministères des affaires étrangères français et indiens, et de l’ITI QMAT.

Une vingtaine de présentations orales sont programmées.
Les orateurs sélectionnés proviennent du monde académique et du monde industriel.
Nous échangerons sur des aspects touchant aux propriétés fondamentales de ces matériaux et à leurs applications, notamment dans le domaine des mémoires et des technologies de l’information.

Plus d’information sur le flyer ci-joint et sur le site du workshop :
https://sites.google.com/view/if-wo2dfm2024/home

Cette journée est ouverte à tous, et gratuite.
Pour des raisons d’organisation, Merci de prévenir avant le 26 juin 12h00 de votre participation par email à dayen@unistra.fr.

Workshop SWING

The goal of this workshop is to gather the French community working in the broad field of magnonics (i.e. physics and technologies of spin waves). This workshop will also serve as a scientific kick-off of the project SWING, whose focus is on applied magnonics, and which is part of the recently funded program PEPR Spin.

Please find extra information (schedule, registration submission) at  https://swing-workshop1.sciencesconf.org/

Séminaire DMONS présenté par Kshirsagar Aseem RAJAN

  1. Light tunable gas adsorption in functionalized metal-organic frameworks: insights from ab initio methods Metal-organic frameworks (MOFs) functionalized with azobenzene, a photo-isomerizing molecule, are capable of light stimulated capture and release of CO2. Using ab initio density functional theory (DFT) based atomistic modelling, the microscopic mechanism behind the light tunable gas uptake in azobenzene functionalized MOF-5 is revealed to be the blocking and unblocking of the metal-node, by distinct geometric configurations of azobenzene. A practical environment-consistent Bethe-Salpeter equation (BSE) approach is used for an accurate description of the photo-excitations of the photo switches to propose strategies for achieving high yields of photo switching. Our study also shows that electronic excitations in the prototype MOF-5 give rise to strongly bound states of electron-hole pair, analogous to organic insulators.
  2. Modulation of magnetization in BiFeO3 using circularly polarized light Dynamic and efficient control of the characteristic spin texture of multiferroic BiFeO3 is attractive for emerging quantum devices. Crystal-field d → d excitations localized on Fe atomic sites in BiFeO3 induce a complex interplay among the spin, charge and lattice degrees of freedom, making them relevant for manipulation of the spin texture. Ab initio methods based on the GW approximation and the BSE are used to characterize localized spin-flip excitations within Fe-3d shell. These excitations are strongly bound and appear deep within the electronic gap. Their spin-content and strong localization are protected by the antiferromagnetic ordering. The underlying crystal symmetry gives rise to chiral spin-flip exciton states localized on distinct Fe centers. These chiral excitons couple selectively to light of a particular circular polarization and are confined to a particular Fe magnetic sub-lattice. As a consequence, net spin- magnetization can be achieved using circularly polarized light coupling with exciton of desired chirality, thereby modulating the antiferromagnetic texture and giving rise to transient ferrimagnetism.
  3. Future directions: Understanding charge-lattice-spin coupling using ab initio methods
    In transition-metal oxides, localized excitons can give rise to a complex interplay of spin-charge-lattice degrees of freedom. I intend to motivate and sketch an investigation of the coupling of these excitons with lattice motion and its relevance for optomechanical control.

Pour tout contact : Mébarek ALOUANI : mebarek.alouani@ipcms.unistra.fr

Webinaire DMONS présenté par M. Benjamin Bacq-Labreuil

Benjamin BACQ-LABREUIL (Institut Quantique de l’Université de Sherbrooke – Canada)

Résumé : 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.

Pour tout contact : Mébarek ALOUANI : mebarek.alouani@ipcms.unistra.fr

Liens de connexion le 05 mars 2024  à partir de 14h50 :

https://cnrs.zoom.us/j/94911816568?pwd=c0JoY2EyU1VJOG5SN2NsQXNDRG81Zz09
ID de réunion: 949 1181 6568
Code secret: 0FaFbn