PhD defense : Satakshi Pandey

Satakshi Pandey (IPCMS / DMONS)

The defense is scheduled for Friday 18 October 2024 at 9.30 am in the IPCMS auditorium

This work was performed under the guidance of Dr. Jean Francois Dayen (DMONS) and Dr. David Halley (DMONS).

Franco-Indian mini-workshop on two-dimensional ferroic materials and devices

This workshop is organised with the support of CEFIPRA, the French and Indian Ministries of Foreign Affairs and the ITI QMAT.

Around twenty oral presentations are scheduled.
Speakers have been selected from both academia and industry.
We will be discussing aspects relating to these materials, their fundamental properties and their applications, particularly in the field of memory and information echnologies.

For more information, you can refer to the attached flyer and the workshop website :
https://sites.google.com/view/if-wo2dfm2024/home

The workshop is open to all, and free of charge.
For organisational reasons, please let me know before 26 June noon of your participation by email ( 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/

Seminar DMONS presented by 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.

Contact : Mébarek ALOUANI : mebarek.alouani@ipcms.unistra.fr

Webinar DMONS presented by M. Benjamin Bacq-Labreuil

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