Séminaire IPCMS présenté par Amélie JUHIN

Oratrice : Amélie JUHIN  (Institut de Minéralogie, Physique des Matériaux et Cosmochimie (IMPMC). CNRS-Sorbonne Université)

Résumé : X-ray spectroscopies performed at synchrotron light sources, such as X-ray Absorption Spectroscopy and Resonant Inelastic X-ray Scattering are powerful tools to study complex materials, due to their chemical selectivity that allows disentangling the respective contributions of different atomic species. In this talk, I will show how the use of incident polarized x-rays (either linear or circular) can allow a deeper understanding of the electronic structure and reveal emergent properties, with a focus on remarkable magnetic nanomaterials: Single Molecule Magnets, bimagnetic nanoparticles, ferrofluids, ultra-thin nanowires. Moreover, I will illustrate how the combination of these spectroscopies with x-ray microscopy can provide valuable information with nanoscale spatial resolution, exemplified by recent results obtained on magnetotactic organisms.

Séminaire AXE 1 “Sciences et Matériaux Quantiques” : présenté par Benjamin Besga

Orateur : Benjamin Besga, ILM Lyon

Résumé : The aim of stochastic thermodynamics is to study small non-equilibrium systems subject to thermal fluctuations. Some results from this field will be illustrated using experiments carried out on opto-mechanical systems, mainly colloidal particles in an optical trap. Using non-equilibrium statistical physics will see how we can accelerate the natural dynamics of a system, shorten the mean first passage time on a target, or measure the forces acting on a non-equilibrium probe. Finally, we’ll ask how we can interrogate the quantum limit of these results by looking at the opto-mechanical coupling of a self assembled supercrystal of quantum dots in an optical trap.

Séminaire DON , axes 1 et 4 présenté par Abdelghani Laraoui

Abdelghani Laraoui (Department of Mechanical & Materials Engineering, University of Nebraska-Lincoln)

Résumé :
Magnetic microscopy based on nitrogen vacancy (NV) centers in diamond has become a versatile tool to detect magnetic fields with an unprecedented combination of spatial resolution and magnetic sensitivity, opening up new frontiers in biological [1] and condensed physics matter research [2]. In this seminar, I will present two examples of using NV magnetic microscopy in both scanning probe microscopy (SPM) and wide-field microscopy (WFM) geometries to study nanoscale magnetic phenomena in different materials. First, I will discuss NV-SPM measurements of antiferromagnetic (AFM) domains switching in Cr2O3 and B-Cr2O3 thin films and device structures [3, 4]. Cr2O3 is an archetypical AFM oxide that permits voltage-control of the Néel vector. In addition, boron doping increases Néel temperature from 307 K to 400 K and allows realizing voltage controlled Néel vector at zero applied magnetic field, a promising finding to AFM spintronics. Then, I will discuss NV-WFM measurements on individual Fe(Htrz)2(trz)](BF4)] (Fe triazole) spin-crossover (SCO) nano-rods of size varying from 20 to 1000 nm [5]. Fe triazole SCO complexes exhibit thermal switching between low spin (LS) and high spin (HS) states which are applicable in thermal sensors and molecular switches. While the bulk magnetic properties of these molecules are widely studied by bulk magnetometry techniques their properties at the individual level are missing. The stray magnetic fields produced by individual Fe-triazole nano-rods are imaged by NV magnetic microscopy as a function of temperature (up to 150 0C) and applied magnetic field (up to 3500 G). We found that in most of the nanorods the LS state is slightly paramagnetic, possibly originating from the surface oxidation and/or the greater Fe(III) presence along the nanorods’ edges [5].

References: [1] I. Fescenko, A. Laraoui, et al., Phys. Rev. App. 11, 034029 (2019). [2] A. Laraoui and K.
Ambal, Appl. Phys. Lett. 121, 060502 (2022). [3] A. Erickson, A. Laraoui, et al., RSC Adv. 13, 178-185 (2023).
[4] A. Erickson, A. Laraoui, et al., to be submitted to Nat. Mat. (2023). [5] S. Lamichhane, A. Laraoui, et al.,
ACS Nano 17, 9, 8694–8704 (2023).

Contact : Valérie Halté (valerie.halte@ipcms.unistra.fr)

Séminaire Axe 3 & DMO présenté par Dr. Chantal Daniel

Dr. Chantal Daniel (Laboratoire de Chimie Quantique, UMR7177 CNRS – Université de Strasbourg)


Coordination compounds, characterized by fascinating and tunable electronic properties, easily bind proteins, polymers, wires or DNA. Upon irradiation these molecular systems develop functions finding applications in solar cells, photocatalysis, luminescent and conformational probes, electron transfer triggers and diagnostic or therapeutic tools. The control of these functions is activated by the light wavelength, the metal/ligands cooperation and the environment within the first picoseconds (ps). After a brief summary of the theoretical background, this contribution reviews case studies, from 1strow to 3rd row transition metal complexes, that illustrate how spin-orbit, vibronic couplings and quantum effects drive the photophysics of this class of molecules at the early stage of the photoinduced elementary processes within the fs-ps time scale range. Besides the “routine” modeling of spectra, computational chemistry may contribute at their interpretation providing valuable information about the various chemical and optical contributions to the (chiro-)optical properties and about their correlation, not only with nuclear arrangement, but also with spin-vibronic effects which are especially relevant in transition metal complexes.

Séminaire Axe 5 : présenté par Dr. Murielle Chavarot-Kerlidou

Orateur : Dr. Murielle Chavarot-Kerlidou (Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux (UMR 5249), F-38000, Grenoble, France.)

Résumé :

Making fuels and chemicals from sunlight and abundant raw materials such as water and CO2 represents a major challenge to meet for a clean energy future. To achieve sunlight-driven water splitting, the integration of molecular H2-evolving catalysts into photoelectrochemical cells is a promising, yet challenging strategy. Our contribution to the field will be highlighted through different examples covering all aspects from catalyst design to the construction of functional water-splitting devices. Photoelectrochemical activity of dye-sensitized NiO photocathodes based on covalent dye – cobalt catalyst assemblies will be discussed in detail, together with some key insights into the factors currently affecting their performances, obtained from advanced spectroscopy and post-operando characterizations


Séminaire AXE 1 “Sciences et Matériaux Quantiques” : présenté par Franklin Luis dos Santos Rodrigues

Orateur : Franklin Luis dos Santos Rodrigues, University of Stuttgart

Résumé :

Quantum thermodynamics allows for the interconversion of quantum coherence and mechanical work. Quantum coherence is thus a potential physical resource for quantum machines. However, formulating a general nonequilibrium thermodynamics of quantum coherence has turned out to be challenging. In particular, precise conditions under which coherence is beneficial to or, on the contrary, detrimental for work extraction from a system have remained elusive. We here develop an approach that allows us to study the far-from-equilibrium thermodynamics of coherence. We concretely derive generalized fluctuation relations and a maximum-work theorem that fully account for quantum coherence at all times, for both closed and open dynamics. We obtain criteria for successful coherence-to-work conversion, and identify a nonequilibrium regime where maximum work extraction is increased by quantum coherence for fast processes beyond linear response

Contact :
Contact : Martin Bowen (martin.bowen@ipcms.unistra.fr)