BEGIN:VCALENDAR VERSION:2.0 PRODID:-//FeRMI - ECPv6.15.20//NONSGML v1.0//EN CALSCALE:GREGORIAN METHOD:PUBLISH X-ORIGINAL-URL:https://fermi.univ-tlse3.fr X-WR-CALDESC:Évènements pour FeRMI REFRESH-INTERVAL;VALUE=DURATION:PT1H X-Robots-Tag:noindex X-PUBLISHED-TTL:PT1H BEGIN:VTIMEZONE TZID:Europe/Paris BEGIN:DAYLIGHT TZOFFSETFROM:+0100 TZOFFSETTO:+0200 TZNAME:CEST DTSTART:20230326T010000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:+0200 TZOFFSETTO:+0100 TZNAME:CET DTSTART:20231029T010000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:+0100 TZOFFSETTO:+0200 TZNAME:CEST DTSTART:20240331T010000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:+0200 TZOFFSETTO:+0100 TZNAME:CET DTSTART:20241027T010000 END:STANDARD BEGIN:DAYLIGHT TZOFFSETFROM:+0100 TZOFFSETTO:+0200 TZNAME:CEST DTSTART:20250330T010000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:+0200 TZOFFSETTO:+0100 TZNAME:CET DTSTART:20251026T010000 END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20240502T103000 DTEND;TZID=Europe/Paris:20240502T120000 DTSTAMP:20260514T162626 CREATED:20240425T083139Z LAST-MODIFIED:20240426T083245Z UID:10349-1714645800-1714651200@fermi.univ-tlse3.fr SUMMARY:L’évolution temporelle de l’information locale. - (Claudia Artiaco / LPT / Seminar). - 2/05/2024\, 10H30 DESCRIPTION:Claudia Artiaco (KTH\, Stockholm) \nSeminar LPT\, 2/05/2024\, 10H30\, 3R1\, seminar room\, 3rd floor \nAbstract :\nDuring the time evolution of many-body systems entanglement grows rapidly\, limiting exact simulations to small- scale systems and small timescales. Quantum information tends\, however\, to flow towards larger scales without returning to local scales\, such that its detailed large-scale structure does not directly affect local observables. This allows for the removal of large-scale quantum information in a way that preserves all local observables and gives access to large-scale and large-time quantum dynamics. To this end\, in [2] we proposed a novel approach that uses the recently introduced information lattice to organize quantum information into different scales [1]\, allowing us to define local information and information currents which we employ to systematically discard long- range quantum correlations in a controlled way. Our approach relies on decomposing the system into subsystems up to a maximum scale and time evolving the subsystem density matrices by solving the subsystem von Neumann equations in parallel. Importantly\, the information flow needs to be preserved during the discarding of large-scale information. To achieve this without the need to make assumptions about the microscopic details of the information current\, we introduce a second scale at which information is discarded while using the state at the maximum scale to accurately obtain the information flow. The resulting algorithm\, which we refer to as local-information time evolution (LITE)\, is highly versatile and suitable for investigating many-body quantum dynamics in both closed and open quantum systems with diverse hydrodynamic behaviors. \nIn this talk\, I will present results obtained with LITE for the energy transport in the mixed-field Ising model and the magnetization transport in the XX spin chain with onsite dephasing\, where we accurately determine the power-law exponent and the energy diffusion constant [2]. Furthermore\, I will sketch how we used the LITE approach to reproduce and interpret the results found in a recent experiment with NV centers in diamonds [3]. Finally\, I will briefly mention how the information lattice can be employed to obtain insightful results about the spatial structure of entanglement in generic many-body quantum states [4]. \nReferences : \n[1] T. Klein Kvorning\, L. Herviou\, and J. H. Bardarson\, Time-evolution of local information : Thermalization dynamics of local observables\, SciPost Phys. 13\, 080 (2022). \n[2] C. Artiaco\, C. Fleckenstein\, D. Aceituno Chávez\, T. Klein Kvorning\, and J. H. Bardarson\, Efficient Large- Scale Many-Body Quantum Dynamics via Local-Information Time Evolution\, arXiv:2310:06036. \n[3] K. Harkins et al.\, Nanoscale engineering and dynamical stabilization of mesoscopic spin textures\, arXiv:2310:05635. \n[4] C. Artiaco\, T. Klein Kvorning\, D. Aceituno Chávez\, L. Herviou\, and J. H. Bardarson\, In preparation\, 2024. URL:https://fermi.univ-tlse3.fr/event/levolution-temporelle-de-linformation-locale-claudia-artiaco-lpt-seminar-2-05-2024-10h30/ LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France CATEGORIES:Events,LPT,Seminars END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20240516T140000 DTEND;TZID=Europe/Paris:20240516T153000 DTSTAMP:20260514T162626 CREATED:20240512T114028Z LAST-MODIFIED:20240513T080440Z UID:10266-1715868000-1715873400@fermi.univ-tlse3.fr SUMMARY:Confined hyperbolic phonon-polaritons in Van der Waals crystals . - ( Sébastien Francoeur / LPCNO / Seminar). - 16/05/2024\, 14H DESCRIPTION:Sébastien Francoeur\, Université Polytechnique de Montréal\, Canada \nSéminaire LPCNO\, seminar room\, INSA\, Build. 27\, Room 2.20 (2nd floor left) \nSummary \nStrong coupling between an electromagnetic wave and a solid-state polar excitation yields hybrid quasiparticles known as polaritons. Owing to their mixed light-matter characteristics\, polaritons express distinctive properties and enable a unique level of control over light\, matter\, and their interactions. Phonon-polaritons results from the coupling of polar transverse optical phonons with light. In strongly anisotropic nanostructures\, they exhibit a hyperbolic dispersion relation from which high-momentum states become accessible\, providing the means to achieve extreme energy confinement and a large density of states enhancements\, thereby providing new functionalities for IR sensing\, low-loss photonic circuits\, and new regimes of light-matter interactions. \nIn this presentation\, I will delve into the science of hyperbolic photon-polaritons\, illustrating their significance and exploring some of their most promising applications. I will also describe why almost all advances in this field have been driven by a single measurement technique for the last two decades: scattering-type near-field microscopy. Then\, I will then undertake two discussions that may play a role in accelerating key developments in this field: \n\nI will experimentally demonstrate how Raman spectroscopy\, a simple\, convenient\, and widely used technique can be used to investigate phonon-polariton dispersion relations\, strong confinement\, and coupling to other solid-state excitations such as excitons.\nI will introduce a promising polaritonic material\, GaSe\, characterized by low-propagation losses and confinement factors matching or surpassing those reported for other Van der Waals crystals.\n\n  URL:https://fermi.univ-tlse3.fr/event/confined-hyperbolic-phonon-polaritons-in-van-der-waals-crystals-sebastien-francoeur-lpcno-seminar-16-05-2024-14h/ LOCATION:Salle 220\, LPCNO\, INSA – LPCNO : 135 avenue de Rangueil\, toulouse\, 31077\, France CATEGORIES:Events,LPCNO,Seminars END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20240521T140000 DTEND;TZID=Europe/Paris:20240521T153000 DTSTAMP:20260514T162626 CREATED:20240520T083842Z LAST-MODIFIED:20240521T061137Z UID:10352-1716300000-1716305400@fermi.univ-tlse3.fr SUMMARY:Incommensurate order with translationally invariant projected entangled-pair states : Spiral states and quantum spin liquid on the anisotropic triangular lattice. - (Juraj Hasik / LPT / Seminar). - 21/05/2024\, 14H DESCRIPTION:Juraj Hasik ( Université d’Amsterdam) \nSeminar LPT\, 21/05/2024\, 14H\, the conference hall\, building 3R4\n \nAbstract : \nSimulating strongly correlated systems with incommensurate order poses significant challenges for traditional finite-size-based approaches. Confining such a phase to a finite-size geometry can induce spurious frustration\, with spin spirals in frustrated magnets being a typical example. Here\, we introduce an ansatz based on infinite projected entangled-pair states (iPEPS) which overcomes these limitations and enables the direct search for the optimal spiral in the thermodynamic limit\, with a computational cost that is independent of the spiral’s wavelength. Leveraging this method\, we simulate the Heisenberg model on the anisotropic triangular lattice\, which interpolates between the square and isotropic triangular lattice limits. Besides accurately reproducing the magnetically ordered phases with arbitrary wavelength\, the simulations reveal a quantum spin liquid phase emerging between the Néel and spin spiral phases. \n[1] Juraj Hasik\, Philippe Corboz\, arXiv:2311.05534 \n\n\n\n  URL:https://fermi.univ-tlse3.fr/event/dynamique-de-la-chiralite-quantique-dans-un-paroi-magnetique-mesoscopique-oleksiy-kolezhuk-lpt-seminar-21-05-2024-14h/ LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France CATEGORIES:Events,LPT,Seminars END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20240524T103000 DTEND;TZID=Europe/Paris:20240524T120000 DTSTAMP:20260514T162626 CREATED:20240522T060341Z LAST-MODIFIED:20240522T093913Z UID:10372-1716546600-1716552000@fermi.univ-tlse3.fr SUMMARY:Fake science : panorama des méconduites et contre-feux pour déjouer les pièges. - (Guillaume Cabanac / Seminar / FeRMI). - 24/05/2024\, 10H30 DESCRIPTION:Séminaires d’ouverture FeRMI\n \nGuillaume Cabanac\, IRIT (Univ. Toulouse III) \nRésumé : \nLe problème du ‘fake’ n’épargne pas la science. Cette conférence dressera un panorama des méconduites contemporaines qui polluent la littérature scientifique\, tout en exposant des contre-feux : actions concrètes à intégrer dans nos pratiques pour détecter les arnaques. Le mur des connaissances érigé par les générations de chercheurs doit être le plus robuste possible. Or\, certaines briques empilées récemment sont friables et menacent l’édifice : les maisons d’édition les plus réputées publient des articles non fiables voire bidons. Fabriqués en masse par des paper mills\, ce sont des assemblages de contenus copiés-paraphrasés-collés (produisant l’expression torturée « péril de la poitrine » au lieu de « cancer du sein »\, par exemple) ou générés par ordinateur (Scigen\, Mathgen\, ChatGPT). Les clients rajoutent leurs noms\, usurpent l’identité de coauteurs inventés\, et soumettent à des revues établies mais infiltrées par des éditeurs véreux qui les acceptent (parfois en masse) en quelques semaines. Ils vont même jusqu’à acheter des citations auprès d’agents qui coordonnent des citation cartels. Ces pratiques dystopiques sont pourtant bien réelles et produisent des contenus non fiables\, qui existent au détriment d’une science qu’on souhaiterait la plus fiable possible. URL:https://fermi.univ-tlse3.fr/event/fake-science-panorama-des-meconduites-et-contre-feux-pour-dejouer-les-pieges-guillaume-cabanac-seminar-fermi-24-05-2024-10h30/ LOCATION:Salle de conférence\, Bâtiment 3R4 CATEGORIES:Events,FeRMIsem,Seminars END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20240527T080000 DTEND;TZID=Europe/Paris:20240531T170000 DTSTAMP:20260514T162626 CREATED:20240528T125431Z LAST-MODIFIED:20240529T063227Z UID:10049-1716796800-1717174800@fermi.univ-tlse3.fr SUMMARY:20th ETSF Young Researcher's Meeting YRM 2024. - 27-31/05/2024 DESCRIPTION:This conference is the yearly event organized by ETSF network of research groups and this year it marks its 20th edition. It aims to gather PhDs students and PostDocs engaged in the interdisciplinary domains\, spanning electronic structure methods\, optical and vibrational properties of materials\, strongly correlated systems\, and machine learning in materials science. Thus researchers without a permanent position at the moment of the conference are encouraged to participate. It is possible to apply for an oral or/and a poster presentation. \nThe scientific program will be divided into 5 sessions: \n\nelectronic structure methods development\noptical properties of materials\nvibrational properties of materials and transport\nstrongly correlated systems and magnetism\nmachine learning in materials science\n\nRegistration is open and will close on April 19th 2024.\nFurther Information will be soon posted on the event website : https://lcpq.github.io/yrm2024/ URL:https://fermi.univ-tlse3.fr/event/20th-etsf-young-researchers-meeting-yrm-2024/ CATEGORIES:Events,LCPQ,Symposium / Congress END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20240528T140000 DTEND;TZID=Europe/Paris:20240528T153000 DTSTAMP:20260514T162626 CREATED:20240519T084433Z LAST-MODIFIED:20240522T093209Z UID:10356-1716904800-1716910200@fermi.univ-tlse3.fr SUMMARY:Électrons lumineux. - (Klavs Hansen / LPT / Seminar). - 28/05/2024\, 14H DESCRIPTION:Klavs Hansen (Université de Tianjin\, république populaire de Chine) \nSeminar LPT\, 28/05/2024\, 14H\, 3R1\, seminar room\, 3rd floor \nAbstract :\nThe emission of thermal electromagnetic radiation from hot molecules and clusters has long been assumed to be a simple matter of vibrational transitions. However\, it is becoming increasingly clear that also electrons can be excited thermally and emit photons. The rates for these emissions can reach microsecond timescales for metal clusters\, more than three orders of magnitude shorter than vibrational IR radiation. Besides often occurring on very short time scales\, the rates also are very molecule-specific ; Every electron counts. In the talk I will present the special features that allow experimental determination of the phenomenon\, and give a tour of some results obtained for molecules and clusters. \n[1] Piero Ferrari\, Ewald Janssens\, Peter Lievens\, Klavs Hansen\, Radiative cooling of size-selected gas phase clusters\, Int. Rev. Phys. Chem. 38 (2019) 405-440 \n[2] C. Walther\, G. Dietrich\, W. Dostal\, K. Hansen\, S. Krückeberg\, K. Lützenkirchen and L. Schweikhard\, Radiative Cooling of a Small Metal Cluster : The Case of V^+_13\, Phys. Rev. Lett. 83 (1999) 3816 \n[3] Shimpei Iida\, Wei Hu\, Rui Zhang\, Piero Ferrari\, Kei Masuhara\, Hajime Tanuma\, Haruo Shiromaru\, Toshiyuki Azuma\, and Klavs Hansen\, Thermal radiative cooling of carbon cluster cations C^+_N \, N = 9\, 11\, 12\, 17 − 27\, Mon. Not. R. Astron. Soc. 514 (2022) 844–851 \n  URL:https://fermi.univ-tlse3.fr/event/electrons-lumineux-klavs-hansen-lpt-seminar-28-05-2024-14h/ LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France CATEGORIES:Events,LPT,Seminars END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20240528T140000 DTEND;TZID=Europe/Paris:20240528T170000 DTSTAMP:20260514T162626 CREATED:20240520T093111Z LAST-MODIFIED:20240522T093658Z UID:10392-1716904800-1716915600@fermi.univ-tlse3.fr SUMMARY:Amélioration de la séparation en impulsion dans les interféromètres atomiques : séquences cohérentes de diffraction de Bragg et accélération de Floquet. - (Tangui Rodzinka / LCAR / Thèse). - 28/05/2024\, 14H00 DESCRIPTION:Soutenance de thèse \nTangui Rodzinka LCAR\, Salle de séminaires\, 3ème étage 3R1 \nsous la supervision d’Alexandre Gauguet\, Baptiste Allard et David Guéry-Odelin \nRésumé:\nMon travail de thèse\, porte sur le développement d’interféromètres atomiques exploitant des condensats de Bose-Einstein manipulés par des réseaux optiques. Je présente diverses méthodes pour créer des interféromètres avec une grande séparation en impulsion entre les deux bras de l’interféromètre. Une première approche repose sur la diffraction d’onde atomique à ordre élevé\, dans le régime dit de quasi-Bragg. Un chapitre est consacré à cette étude\, mettant en évidence l’importance des transitions mulphotoniques non résonantes sur les signaux d’interféromètres. Le chapitre suivant décrit un schéma de séparatrices atomiques\, fondé sur une succession d’impulsions π qui transfert chacune 2ℏk. Nous avons ainsi mis en évidence un nouveau régime d’accélération particulièrement efficace grâce à un phénomène d’interférence destructive entre les pertes. Cette méthode a permis la réalisation d’un interféromètre avec une séparation de 200 impulsions de recul. Enfin\, le dernier chapitre de mon manuscrit introduit une nouvelle technique exploitant le formalisme de Floquet\, qui généralise les séparatrices atomiques précédentes ainsi que celles fondées sur les oscillations de Bloch. Pour préparer de manière optimale les états de Floquet transportés par le réseau optique\, nous avons mis en œuvre des techniques de contrôle optimal. Cette approche a permis de démontrer expérimentalement des interféromètres avec une séparation en impulsion de 600ℏk\, avec une visibilité de 20%. Ce résultat représente la plus grande séparation en impulsion obtenue dans un interféromètre. Les séparatrices atomiques développées dans cette thèse peuvent potentiellement améliorer les mesures de la constante de structure fine et la sensibilité des capteurs inertiels exploitant des techniques d’interférométrie atomique. Par ailleurs\, ces séparatrices ouvrent la voie à des interféromètres présentant une très grande séparation spatiale. Ces interféromètres suscitent un intérêt croissant en physique fondamentale\, offrant diverses possibilités pour tester la relativité générale\, la neutralité de la matière\, ainsi que des modèles de matière noire. L’objectif à plus long terme de l’expérience sur laquelle j’ai travaillé consistera à effectuer des tests de la neutralité de l’atome en utilisant une nouvelle méthode basée sur la phase d’Aharonov-Bohm. Nous prévoyons une amélioration de plusieurs ordres de grandeur par rapport aux limites actuelles. URL:https://fermi.univ-tlse3.fr/event/amelioration-de-la-separation-en-impulsion-dans-les-interferometres-atomiques-sequences-coherentes-de-diffraction-de-bragg-et-acceleration-de-floquet-tangui-rodzinka-lcar-these-28-05-202/ LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France CATEGORIES:Events,HDR / Thesis,LCAR END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20240529T093000 DTEND;TZID=Europe/Paris:20240529T130000 DTSTAMP:20260514T162626 CREATED:20240529T050004Z LAST-MODIFIED:20240529T063122Z UID:10388-1716975000-1716987600@fermi.univ-tlse3.fr SUMMARY:Theoretical study of superfluid helium nanodroplet dynamics: cluster formation\, ion solvation\, Coulomb explosion\, and quantum vortex detection and nucleation. (Ernesto García Alfonso / LCAR / Thèse). - 29/05/2024\, 9H30 DESCRIPTION:Soutenance de thèse \nErnesto García Alfonso LCAR\, Salle de séminaires\, 3ème étage 3R1 \nlist of the jury members: \n\nMme Nadine HALBERSTADT : Directrice de thèse (CNRS Occitanie Ouest)\nM. Lionel POISSON Rapporteur (CNRS\, Institut des Sciences Moléculaires d’Orsay)\nMme Alexandra VIEL Rapporteuse (Institut de Physique de Rennes)\nM. Marcel MUDRICH Examinateur (Aarhus University\, Denmark)\nMme Pina ROMANIELLO Examinatrice (Laboratoire de Physique Théorique\, Toulouse )\nM. Manuel BARRANCO Invité (Facultat de Física\, Universitat de Barcelona)\nM. Marti PI PERICAY Invité (Facultat de Física\, Universitat de Barcelona)\n\n  \nSummary:\nSeveral dynamical processes involving Helium-4 nanodroplets (HNDs) are studied theoretically\, in relation with experiments. HNDs are clusters of several hundred to several hundred billions of 4He atoms which exhibit remarkable properties: very low temperature\, T∼0.4K\, superfluid properties\, ability to pickup any dopant\, weak interaction with any atom or molecule. The studied processes reflect the two main interests in HNDs: characterizing superfluid properties in a finite-size system (quantum vortex nucleation and detection)\, and using HNDs as an ideal environment to study dopant spectroscopy and dynamics (clustering\, ion solvation\, and Coulomb explosion). Extensive simulations are conducted using 4He-Density Functional Theory (4He-DFT) and its time-dependent version (4He-TDDFT). This approach can successfully simulate the equilibrium and dynamics of droplets of several thousand of atoms and provide detailed insight into the structural dynamics of the entire system which is not accessible experimentally: visualization of solvation shells\, nature of helium droplet excitations. Rare gas (Rg) cluster formation is studied inside HeN under realistic conditions where one Rg atom collides with a solvated n-atom cluster to form the (n+1)-atom cluster. The 4He-DFT simulation results are compared to those of approximate atomistic approaches. Although quantum and superfluidity effects are better described with 4He-TDDFT\, several common features are demonstrated. The most stable gas phase configuration is usually not produced\, but an isomer with fewer bonds instead\, and/or more dilute structures because of the rigidity of the helium solvation shell around the Rg atoms. The sinking of alkali (Ak) cations in HNDs is simulated in parallel with experimental investigations in the group of Stapelfeldt (Aarhus)\, in complement to earlier studies on Na+ sinking. It aims at shedding some light on the primary steps of solvation\, by suddenly ionizing the alkali atom sitting in a dimple at the droplet surface. The build up of the first solvation shell around the ions is shown to be progressive\, pointing to a Poissonian mechanism in which each He atom binds independently to the ion. For the lighter alkalis\, the solvation shell is incomplete at the end of the dynamics\, suggesting a kinetic rather than thermodynamical control of its formation. Coulomb explosion simulations of Ak2 molecules initially sitting at the droplet surface and suddenly ionized are conducted in order to understand the effect of the HNDs on Ak2++ fragmentation dynamics. The corresponding experiment in Stapelfeldt’s group in Aarhus aimed at measuring the proportion of triplet to singlet state in the formation of Ak2\, and at imaging the vibrational wave function. Several parameters are examined in the simulations: droplet size\, zero point motion of Ak2 vibration\, and orientational distribution of Ak2 on the droplet surface. The results validate the experimental approach\, and evidence an unexpected curvature of the ion trajectories which could be used to measure droplet sizes individually\, something that has only been possible up to now for very large sizes (by X-ray diffraction). The nucleation of quantum vortices\, a characteristic of helium superfluidity\, has been revealed in very large droplets (VLD) and attributed to angular momentum created by friction of the liquid in the nozzle prior to expansion and cooling. Here droplet-droplet collisions are explored as an alternative mechanism. The results show the nucleation of quantum vortices at indentations of the merged droplet\, a mechanism general for all droplet sizes. However\, no signature has been found to detect vortices in smaller droplets so far. In this work\, fluorescence absorption or excitation spectroscopy of alkali atoms is proposed: a vortex is shown to shift and broaden the alkali spectrum. The effect could be measurable above the first excited states. URL:https://fermi.univ-tlse3.fr/event/theoretical-study-of-superfluid-helium-nanodroplet-dynamics-cluster-formation-ion-solvation-coulomb-explosion-and-quantum-vortex-detection-and-nucleation-ernesto-garcia-alfonso-lcar-these/ LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France CATEGORIES:Events,HDR / Thesis,LCAR END:VEVENT END:VCALENDAR