The rubidium 87 quantum gas experiment at the Laboratoire de Physique des Lasers produces degenerate gas samples in a quadrupole magnetic trap dressed with a radio frequency field. In this experiment, the atoms are located near an isomagnetic ellipsoidal surface of the inhomogeneous static field. In the presence of gravity, this ellipsoidal trap allows a two-dimensional confinement in a smooth...
Spin torque nano-oscillators (STNO) are nanoscale devices based on a magnetic tunnel junctions. Such STNOs generate microwave voltage signals upon injection of a DC current. The phase dynamics of weakly coupled arrays of STNOs and/or coupling of STNOs to an external RF signal (injection locking), can be harnessed to develop novel hardware approaches for unconventional computing [1]. When...
Contrairement au soliton brillant, les solitons à respiration présentent un comportement oscillatoire périodique. L’utilisation des fibres optiques a grandement facilité leur observation: l’interaction sur une grande distance entre la non-linéarité Kerr et la dispersion, en la quasi-absence de dissipation a ainsi permis la caractérisation fine des solitons à respiration d’Akhmediev, de Ma ou...
Life cannot exist or evolve without liquid water, which is a substance composed of a molecule that is both simple and complicated to understand. In Latin, it is called "Aqua via". Water is a universal solvent because of its polarity and hydrogen bonds, which allow many chemical substances such as salts and ions to dissolve. Therefore, water models are studied to simulate its structural and...
The ultra-low temperature cryogenics industry faces many challenges, such as the emergence of new players and the rise of quantum computing, which is now the focus of industrial and policy concerns. With the development of quantum computing, the most complex problems could be solved much faster because quantum computing will offer an unprecedented level of computing power.
In order to meet...
La recherche de moments dipolaires électriques permanents (EDM) de particules élémentaires offre des contraintes sur la physique au-delà du modèle standard, en particulier sur les brisures de symétrie CPT. Je présenterai brièvement l'état actuel du projet << Vers un EDM avec atomes et Molécules en MAtrice >> (EDMMA) dont le but est d’améliorer la sensibilité expérimentale à l'EDM de l'électron...
On June 23rd 2022, BepiColombo performed it’s second gravity assist maneuver (MFB2) at Mercury. Just like the first encounter which took place on October 1 2021, the spacecraft approached the planet from dusk-nightside to dawn-dayside to an extremely close distance within about 200 km altitude above the planet’s surface. This distance is closer than the two orbiters of BepiColombo will orbit...
Exciton-polariton are bosonic quasi-particles that arise from the strong coupling between light and matter. They are typically formed in a quantum well embedded in an optical microcavity, from the interaction between quantum well excitons and cavity photons. Under non-resonant pumping, it is shown that exciton-polariton can form a Bose-Einstein condensate (BEC) [1]. This out of equilibrium BEC...
Nous présenterons au lecteur le monde fascinant des ondes breathers au travers d'une simple vue d’ensemble du sujet, en passant par les faits historiques clés et les progrès de la recherche, impliquant différents domaines tels que la théorie des ondes non-linéaires, l'optique, et l’hydrodynamique.
Les ondes non-linéaires instables apparaissent dans une variété de systèmes physiques et...
Gliomas are a type of brain tumor characterized by highly invasive cells, capable of migrating significant distances while remaining under the MRI detection threshold. This invasive behavior often leads to inevitable tumor recurrence following treatment. Radiotherapy is a key component in this treatment, involving the administration of fractionated doses according to a precise...
In the framework of ultra-cold chemistry, where reactions can be studied in well-defined quantum states, collisional phenomena between cations and neutral atoms are still not fully understood. Widely used semi-classical capture models, such as the one of Langevin [1], fail in some cases in predicting correctly rate constants associated to the charge transfer between two such species. The...
The advent of ground-state controlled ultracold dipolar molecules in dense gases has opened many exciting perspectives for the field of ultracold matter. When the molecules are dipolar, their extremely controllable properties have inspired many theoretical proposals for promising quantum applications, such as quantum simulation/information processes, quantum-controlled chemistry and test of...
La coacervation complexe est un processus thermodynamique qui induit la formation de deux phases liquides, à l’équilibre. Ce phénomène a été observé dans différents compartiments cellulaires et permet notamment de concentrer localement des biomacromolécules : protéines, ARN et/ou enzymes. Malgré les intérêts multiples de la coacervation, il est encore difficile de comprendre et prédire les...
Absorbing phase transitions, where a system goes from from a dynamic `alive' state to a static 'dead' state from which there is no return, are ubiquitous in many areas of research, including epidemiology, ecology, and physics. Here, we use computer simulations to explore an absorbing phase transition in a simple model consisting of granular beads in a quasi-two-dimensional vibrating container....
Dark matter is one of the greatest mysteries in contemporary physics. It constitutes a significant portion of the universe, yet its nature remains unknown. Recent years have witnessed research efforts dedicated to understanding its properties, employing both direct and indirect detection experiments. In light of these efforts, the iDMEu project was developed to foster collaboration among...
In standard cosmological models, inflation is driven by a quantum field, the inflaton, whose constant energy density drives the superluminal expansion of the universe [1]. When inflation stops, the universe has an extremely low density but the inflaton field starts to oscillate around its minimum of energy and decays into entangled pairs of particles [2]. This is known as the pre-heating...
We simulate the Coulomb explosion upon double ionisation of alkali dimers (Ak2, Ak≡ Na, Rb, Cs) bound to the surface of a superfluid droplet of 1000 to 50000 4He atoms, using 4He-TDDFT (Francesco et al. [1]) This work was motivated by the experiment of Kristensen et al. [2], who used this process to deduce the abundance ratio of neutral dimers formed on the surface of a helium nanodroplet in...
The motion of an ion in water is strongly affected by frictional effects from the surrounding solvent. Various theory have been put forward to characterize those effects and they feature a separability between mechanics part (short-ranged or Lennard-Jones forces) and dielectric part from the long range electrostatics. We study numerically the time-dependent friction from the water on...
Helium nanodroplets are intriguing entities, these superfluid physical objects were made at the end of the 20th century and share common features with Bose-Einstein condensates.
With a temperature of only 0.38K, they are now playing a major role as a host for atoms, molecules and clusters for preparing cold samples and in the formation of atomic/molecular clusters. Their high thermal...
La dynamique de photoionisation ultrarapide dans les molécules est au centre d’intérêt de nombreux travaux qui tirent parti du développement de sources de lumière attoseconde dans l'ultraviolet extrême (XUV), et d’expériences pionnières de type pompe-sonde (XUV+IR) sur des cibles atomiques, moléculaires ou solides visant à caractériser les délais de photoionisation induite par absorption d’un...
Le microorganismes sont capables de se disséminer de différentes
manières, sous forme de spores dans l'air, en nageant à l'aide de
flagelles ou cils dans l'eau, ou encore en rampant sur des substrats
solides. Nous avons découvert que les bactéries de l'espèce Bacillus
subtilis parviennent à provoquer le glissement de gouttes d'eau à la
surface d'hydrogels, faisant ainsi bouger la colonie...
Abstract:
FeCu alloys at different milling times (1-48 hours) were synthesized using high energy planetary ball mill method. The synthesized nanosized powders were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM) techniques. Results showed that the ball milling causes the overall structural disorder and the particle...
De nombreux matériaux présentent une microstructure qui est le résultat d'une séparation de phase (décomposition spinodale) suivie d'un murissement (augmentation de la taille caractéristique qui permet une diminution des interfaces). Nous nous sommes intéressés au effets des détails de la cinétique du murissement sur les propriétés de la microstructure et sur sa nature.
Des simulations...
L’équation de Schrödinger non linéaire régit l’évolution des ondes dans de nombreux domaines non linéaires tels que l’hydrodynamique, la physique des plasmas, les condensats de Bose-Einstein et l’optique fibrée. Dans ce dernier cas, l’onde subit des changements dans un milieu dispersif combiné à un déphasage non linéaire dépendant de l’intensité. Le processus clé sous-jacent est le mélange à...
Event-driven molecular dynamics (EDMD) simulations have proven to be particularly robust for simulating hard sphere systems. They offer insights into a variety of self-assembly processes, among which crystal nucleation remains a topic of interest. Experimentally, colloidal hard spheres have been achieved with great success, but open questions remain regarding discrepancies in nucleation rates...
In this poster I will present some recent advances in exciton-phonon coupling in low-dimensional systems. I will describe the role of dimensionality in the formation of excitons and their interaction with vibrational modes. I will show how this interaction leads to a finite lifetime for excitons and the appearance of phonon-assisted replicas in the luminescence spectra. Results will be...
Revealing universal behaviors in different systems is a hallmark of statistical physics. At equilibrium, simple models, like the Ising model, have been essential in understanding the critical properties of a whole class of systems. Reversely, a clear description of the universal properties of several non-equilibrium systems remains elusive. In this context, the Kardar-Parisi-Zhang (KPZ)...
Two-dimensional electron gases (2DEG) at SrTiO3 (STO)-based oxide interfaces gained a wide interest not only from the fundamental aspect but for their potential usage in technological applications.1-2 A rich variety of emergent phenomena such as quantum Hall effect, Shubnikov-de Haas oscillations, Rashba effect, 2D superconductivity, inverse Edelstein effect etc. were observed at such...
Oxide heterostructures are regarded as promising platforms for the next generation of electronic devices, displaying straightforward properties like high carrier mobility to exotic functionalities like multiferroicity. In polar heterostructures, the interfacial electric field can produce a two dimensional electron gas (2DEG). The broken inversion symmetry results in Rashba spin-orbit coupling...
For the past few years, 2D ferroelectric materials have attracted strong interest for their potential in future nanoelectronics devices. The recent discovery of 2D ferroelectricity in twisted layers of insulating hexagonal boron nitride [1-3], one of the most used 2D materials, opened the route to its integration into complex van der Waals heterostructures combining hybrid properties. Indeed,...
Ozone (O3) is an important molecule playing a pivotal role in Earth’s atmosphere and climate chemistry through atmospheric oxidation. Accurate measurements of O3 molecular line frequencies and shapes over a wide spectral range through laser spectroscopy open the way to improve the determination of atmospheric ozone mixing ratios or abundance profiles in the atmosphere.
In 2018, we have...
Quantum dots (QD) constitute a novel generation of fluorescent probes due to their confined size in the 1-10 nm range. In this field, nanosensors sensitivity is of pivotal importance to target biomolecules. We focus here on the optimize grafting of organic ligand-coated CdTe and CdSe/ZnS coreshell type QDs monolayers on glass surfaces to address the environmental problem and cost of...
A variety of molecular solid hydrogen phases can be synthesized with diamond anvil cells between 100 and 400 GPa [1]. Raman and Infrared spectroscopy measurements have allowed the determination of the hydrogen phase diagram in this pressure range [2]. However, structural information on these phases is currently missing because of the low scattering efficiency of the hydrogen atom in X-ray...
We study the inertial effects on contact line dynamics for liquid in partial wetting on several surfaces with low hysteresis. These surfaces have an imposed oscillatory motion entraining the liquid (whose upper part is pinned on an adhesive surface). We measure the dynamic contact angle as a function of the triple line velocity and relate the emerging hysteresis cycles to the oscillations and...
Water plays an important role in the structure and properties of biomolecules. For example, hydrophobic interactions provide the dominant force driving protein folding. One native structure of the protein is encoded in the amino acid sequence because of these interactions [1]. Isolation of biomolecules in the gas phase removes all interactions with the solvent, but also enables stepwise...
Chronic infections of the human immunodeficiency virus (HIV) create a very complex co-evolutionary process, where the virus tries to escape the continuously adapting host immune system. Quantitative details of this process are largely unknown and could help in disease treatment and vaccine development. Here we study a longitudinal dataset of ten HIV-infected people, where both the B-cell...
Les stratégies ascendantes pour la production de nanostructures bien définies reposent souvent sur l'auto-assemblage de particules colloïdales anisotropes (nanofils, nanofeuillets). Ces briques de base peuvent être obtenues par exfoliation dans un solvant de cristaux de basse dimensionnalité. Pour optimiser l’obtention de ces particules anisotropes, la détermination du mécanisme d’exfoliation...
We present a room temperature STM study of dynamics of the quasi-liquid perylene monolayer formed on Ag(110) under thermal equilibrium. We observe that the thermodynamic balance of the molecule-molecule and molecule-substrate interactions generate a compact two-dimensional (2D) quasi-liquid state established by the mobile perylene molecules dynamically distributed into three distinct motion...
Un cristal liquide est un composé possédant une ou plusieurs phases intermédiaires entre la phase liquide usuelle et la phase cristalline. En phase nématique, les molécules sont en moyenne dirigées selon une direction donnée, le directeur n. Récemment, de nouvelles molécules cristal-liquides de forme courbée ont été synthétisées et suscitent un grand intérêt car elles présentent des phases...
Laboratoire Kastler Brossel, Sorbonne Université, ENS, CNRS ; 4 place Jussieu, Case 74, 75005 Paris, France
Département de Physique, Univ EVRY Université Paris Saclay, rue du père André Jarlan, 91025 Evry, France
The work presented in this poster focusses on the stabilisation of a mid-IR laser against a frequency comb which is optically locked to the ultrastable REFIMEVE signal and on...
The dynamics of macromolecules at solid-liquid interfaces is key to a number of surface phenomena such as functionalization, transport in porous media or friction. In the recent years, novel single-molecule microscopy techniques based on total internal reflection fluorescence microscopy have allowed to probe the in-plane equilibrium diffusion dynamic of macromolecules at the single chain...
The experimental technique of fluorescence light measurement is used for indirect observations of ultrahigh energy cosmic rays. The aim is to reconstruct the shower cascade curve and estimate the primary particle energy and its arrival direction. For this purpose, the development of extensive air showers, initiated by different primary particles entering the Earth’s atmosphere with extreme...
We are surrounded more and more by environmental noises. Some of them have been extensively studied since long time, their nocivity have been well known. For example, excessively strong acoustic noises in the audible range lead to damage of the hearing system.
In contrast, various harmful effect of electromagnetic noises are not unanimously accepted by the scientific community. The related...
The aim of the work that I will present in the poster is to study the superfluid dynamics of a quantum gas trapped on the curved surface of a bubble-shaped trap. First I will present a new trapping configuration and loading procedure for the realization of the bubble trap, based on an hybrid quadrupole-dimple trap. This helps reducing the superfluid excitations during the loading of the bubble...
Thanks to recent experimental advances, it is now possible to study the transport of water and ions confined up to one molecular layer. An example of such a system is the 2D nanoslit, made of sheets of 2D materials, like graphene or hexagonal boron nitride. Experimental measures of the ionic conduction under an external electric potential proves that the ionic transport is non linear and...
L’énergie solaire est une énergie renouvelable, abondante et peut être considérée comme l’une des énergies du futur la plus prometteuse. La nature, au cours de l’évolution a modelé un système très efficace pour utiliser cette énergie : La photosynthèse. La photosynthèse transforme le dioxyde de carbone et l’eau en présence de la lumière en sucres et oxygène .
Cette réaction trompeusement...
Le dichroïsme circulaire de photoélectrons (PECD) permet de mesurer l’asymétrie avant/arrière de la distribution angulaire des photoélectrons par rapport à l’axe de propagation de la lumière suite à l’ionisation d’une molécule chirale par une lumière polarisée circulairement.[1] Le PECD est une méthode autorisée dans l’approximation dipolaire électrique, le rendant beaucoup plus intense,...
L'un des principaux défis de la spintronique est la génération et la détection efficaces des courants de spin, ouvrant la voie à des dispositifs ultra-rapides et à faible consommation d'énergie pour le stockage et le traitement des données. Alors que la plupart des premières approches proposées souffrent de problèmes de désadaptation d’impédance et de dissipation d'énergie [1], le pompage de...
L'expérience GiantMol vise à développer une méthode de détection non destructive pour les macromolécules chargées en utilisant des nuages d'ions refroidis par laser. Cette nouvelle approche repose sur la modification de l'équilibre thermodynamique d'un nuage d'ions piégés refroidis par laser lorsqu'il est traversé par un projectile chargé et massif. L'objectif est de détecter le projectile en...
The analysis of the far wings spectral broadening of the alkali D1(np 2P1/2− ns 2S1/2 )and D2 (np 2P3/2− ns 2S1/2)lines Provoked by interaction with rare gas atoms prove their importance in design and construction of new types of lasers as well as in the investigation of the chemical and physical properties of brown dwarfs and extrasolar planets.
This work deal with the pressure broadening...
Our work focuses on hybrid optomechanical resonators embedding quantum wells (QW). A microscale mechanical Gallium Arsenide disk supports high Q optical whispering gallery modes (WGM) that strongly couple to the QW excitons, forming WGM polaritons. The resulting confinement in a sub-micron volume of mechanical, optical and excitonic modes, generates a tri-partite situation of interest for...
L’expérience GBAR (Gravitational Behaviour of Antihydrogen at Rest) installée sur l'anneau du décélérateur d'antiprotons -AD- au CERN reprend la proposition de J. Walz et Th. Hänsch [1] qui vise à étudier la chute libre d'un atome d'antihydrogène préparé au repos [2]. Cette expérience implique deux ions piégés dont l’un, l’ion Be+, est refroidi par laser et l’autre, l’ion 𝐻̅+, est refroidi par...
CrCl3 is a van der Waals material particularly interesting for its magnetic properties. In each layer, the Cr atoms are coordinated in an octahedral configuration to the neighboring Cl atoms (Cr-Cl bonds are off-plane and the Cr atoms form a honeycomb lattice). The Cr atoms are coupled ferromagnetically via super-exchange and their magnetic moments lie in-plane. Its magnetic properties have...
Real-time dynamics of the electronically excited open-ring isomer of 1,2-bis(2-methylbenzo[b]thiophen-3-yl)perfluorocyclopentene (BTF6) and 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene (PTF6) molecules was investigated using a set-up that associates a molecular beam, femtosecond lasers and a velocity map imager. The molecules were either free in the gas phase or bound to an...
Des observations clés récentes avec les télescopes spatiaux Spitzer et Hubble nous ont donné un aperçu réel de la composition des systèmes planétaires extra-solaires grâce à la détection spectroscopique de traces de métaux lourds dans les atmosphères des naines blanches froides DZ. Ces caractéristiques observées sont maintenant attribuées à la présence de matériaux planétaires rocheux comme...
We aim at investigating the motion of adsorbates on metallic surfaces with entirely quantum calculations. We want to see what quantum phenomena are likely to occur during this motion, which can be related to diffusion. The Multiconfigurational Time Dependent Hartree (MCTDH) method will be used to obtain the quantum dynamics from first principle calculations. These calculations will help us to...
We study the interactions between two Rb atoms and one Rb$^+$ ion from a quantum chemistry perspective, considering the Rb$_2$+Rb$^+$ and Rb$_2^+$+Rb arrangements. These interactions are relevant for the fundamental chemistry, sympathetic cooling, and three-body recombination (TBR) processes at ultra-low temperatures observed in hybrid ion-atom experiments for homo- and hetero-alkali ion-atom...
The ceramic brittleness is due to pre-existent micro-cracks that become unstable under the effect of a stress and leads to the fracture of the specimen. However, alumina presents a crack growth resistance that translates stable crack propagation before the fracture. In this case, the material toughness is not constant but increases with the crack extension. It depends on the crack extension da...
General relativity has been tested with exquisite accuracy in the Solar system. However, tests in the strong-field regime require a compact object. This is why a new era of strong-field tests opened up in 1974 with the discovery of the first binary neutron-star system by Hulse and Taylor in 1974 for which they both obtained the 1993 Nobel prize.
I will briefly review tests of general...
Structure, hyperfine, thermal stability, and magnetic properties of the mechanically alloyed Fe47.5Co50Ni2.5 (Fe47.5) and Fe50Co47.5Ni2.5 (Fe50) powders were investigated by using X-ray diffraction (XRD), 57Fe Mössbauer spectrometry, differential scanning calorimetry, and vibrating sample magnetometer, respectively. The XRD results show the existence of bcc α-Fe type, bcc FeCo, and hcp Co-type...
The real-time dynamics of DABCO-argon clusters is investigated in a femtosecond pump-probe experiment where the pump excites DABCO to the S$_1$ state within the argon cluster. The probe operates by photoionization and documents the energy and angular distributions of the resulting photoelectrons. The dynamics is followed up to 500 ps. A multiscale dynamics is observed. It includes a short...
Topological defects such as vortices, dislocations or disclinations are fingerprints of order parameters resulting from broken symmetries. We introduce the new concept of topological defects of a higher order, that we propose to call metadefects, using as a generic example tangles of dislocations in cholesterics.
Tangles of dislocations are generated by a tensile strain in a cholesteric...
We propose a method to engineer repulsive long-range interactions between ultracold ground-state molecules using optical fields, thus preventing short-range collisional losses. It maps the microwave coupling recently used for collisional shielding onto a two-photon transition, and takes advantage of optical control techniques. In contrast to the previously proposed one-photon optical shielding...
"Seuls 5% de la matière et de l'énergie de l'univers sont connus ; 25% d'une matière noire inconnue (6 fois plus abondante que la matière ordinaire) et 70% d'une mystérieuse énergie noire manquent à l'inventaire." Notre communication, ouverte à la critique, propose une solution simple à ces défis en considérant l'univers comme un milieu réfringent (1). Pour cela, si la valeur actuelle c0 de la...
In this poster, we present a framework to analyze universal constraints on growth, lineage and selection for cell populations.
Dark Matter research constitutes a significant scientific challenge, motivated by several gravitational phenomena that cannot be explained by visible matter alone. Dark matter makes up almost 85% of the mass and 27% of the total energy density of the Universe, which is five times higher than that of ordinary matter. To explain the various observations, several dark matter candidates have...
Dans un processus de réactions génératrices de chaleur, une fois amorcée, la synthèse se produira grâce à l’énergie libérée par la réaction entre les réactifs, ne nécessitant alors aucun apport supplémentaire d’énergie. La particularité que présente ce type de réaction, telle que la synthèse auto propagée ne réside pas dans le fait qu’elle permet de synthétiser des produits très purs, mais de...
Avec le perfectionnement des télescopes, la détection de molécules dans le milieu interstellaire a connu de grands progrès. En 1974, la méthylamine fut découverte dans le nuage interstellaire Sagittarius B2, soit 4 ans après la détection de l’eau dans ce même nuage.[1,2] Également, c’est en 2006 que l’on découvre l’acétamide, produit impliquant la formation d’une liaison de type peptidique.[3]...
Many soft matter materials evolve through surface tension driven phase separation. During this process the growth of domains can occur via material transfer through the continuous phase. A particular example is foams, which coarsen as gas diffuses between bubbles due to differences in Laplace pressure. We study the temporal evolution of foams where the continuous phase is a viscoelastic fluid...
Detection of several molecules in the gas phase in the coldest regions of the interstellar medium, ISM (molecular clouds, protoplanetary disks…), has motivated intense laboratory experiments with the purpose of quantification and a better understanding of indirect desorption processes1. Condensation of gas-phase atoms and molecules on the surface of cold dust grains in these regions are known...
Traditionally, memory writing operations proceed one bit at a time, limiting the storage capacity of materials. A way to overcome this limitation would be to write several bits at once. Although quasi-static operations are typically used for bits manipulation, they are known to reduce the memory capacity of a system. To address this issue, we introduce a model framework for dynamical memory...
La caractérisation d’une source d’ions à structure coaxiale pour son intégration dans une colonne à faisceaux d’ions focalisés est en cours au CINaM. La structure coaxiale consiste en une fuite de gaz entre un compartiment haute pression et un compartiment basse pression. Elle comporte un fil de tungstène inséré dans un capillaire en inox. Le fil de tungstène est taillé en pointe très fine du...
Dans l'industrie électronique, les semi-conducteurs III-N sont fréquemment utilisés pour créer des composants tels que des transistors à effet de champ, des diodes électroluminescentes et des cellules solaires. Les performances et la fiabilité de ces dispositifs électroniques peuvent être influencées, entre autres, par les propriétés thermiques de ces matériaux, telles que les coefficients de...
