Ten years of research & innovation in two-dimensional materials-based spintronics: highlights & future

Stephan Roche

ICN2 and BIST, Barcelona, Spain

This talk will review more than a decade of intense efforts to explore the potential of graphene and two-dimensional materials for spintronic applications. Along the way, plentiful of unique properties have emerged making topological materials an enabling platform for innovation in advanced electronics, spintronics or quantum technologies. We will overview the milestones and highlight the unprecedented properties which have been revealed to date and point out current challenges and opportunities for harnessing quantum matter to design novel quantum technologies.


C12 Quantum Electronics: Leading the next materials leap in quantum computing

Alice Castan

C12 Quantum Electronics

C12 Quantum Electronics is a spinoff of the Physics Laboratory of the Ecole Normale Supérieure (LPENS) in Paris, France. The company was founded in the beginning of 2020 with the ambitious goal to build a carbon nanotube (CNT)-based quantum processor. From a team of a few scientists at its earliest stage, C12 grew – after securing a $10M seed round in 2021 – into a multiteam organization with over 30 employees. The technology developed at C12 is based on over a decade of research led by CNRS research director Takis Kontos at the LPENS on the use of CNTs in hybrid quantum circuits.

An ultra-clean CNT is directly transferred onto a microchip, where it is suspended over a series of gate electrodes that allow the formation of a double quantum dot (DQD) in which a single electron can be trapped. The spin of the electron is then addressed through coupling to a superconducting microwave circuit. The unique possibility of selectively embedding the CNT or removing it from the microchip at the end of the chip fabrication process provides an opportunity to preselect the qubits integrated in our processor, which is absent from other spin qubit-based quantum computing technologies.

This seminar will give an overview of C12 as well as a presentation of the technology developed in its Paris-based laboratory. Focusing on the core material that makes this technology uniquely promising, we will show how the atomic structure, cleanliness, and isotopic purity of the CNTs acting as the spin qubit hosts influence the performance of the device and how measuring and controlling these parameters can help achieve record fidelity and scalability.

Segregation within bi-metallic nanoparticles at the atomic scale through a combined theoretical and experimental approach


The analysis of nanoparticles (NPs) on a nanometric scale for applications in real-life conditions remains a considerable challenge at the present time. In this context, the use of bi-metallic NPs is strongly envisaged in the field of catalysis, with the function of promoting and accelerating the kinetics of surface chemical reactions. It is therefore essential to describe the structure and chemical composition of the surfaces, which interact directly with the surrounding medium in which the NPs are immersed. In the context of this thesis, we have developed a combined theoretical and experimental approach at the atomic scale, with the aim of studying two types of alloy in particular: Gold-Copper (Aux-Cu1-x) and Nickel-Aluminium (Nix-Al1-x).
Using laser synthesis of 5 nm facetted octahedral Aux-Cu1-x NPs and aberration-corrected electron microscopy observations in probe mode, we developed a method for analyzing the chemical composition of each atomic plane. In this way, we have demonstrated a strong segregation effect of gold on the surface, as well as different concentration profiles within the NPs depending on the chemical order (ordered or disordered). In the case of an ordered Au0.5Cu0.5 composition of L10 phase, we have characterized a structure rarely observed until now, corresponding to the presence of the three possible variants of L10 phase within the same particle. In parallel, atomic-scale simulations have enabled more precise analyses to be carried out, considering infinite plane stacks and NPs of different sizes and compositions.
The excellent agreement between simulations and experimental analyses strengthens the relevance of our results and demonstrates the importance of this dual approach, which we subsequently applied to the study of the surface properties of Nix-Al1-x-type NPs. First, we optimized the synthesis parameters to obtain NPs with defined sizes and compositions. Experimental surface analyses coupled with atomistic simulations enabled us to observe a hitherto unseen phenomenon. Indeed, an almost complete segregation of the aluminum appears until the formation of NPs adopting a core (Nickel) – shell (Aluminum) structure, for all the concentrations studied, thus preventing any alloy formation. This is all the more surprising given that, in the bulk state and for a composition of 50% nickel and 50% aluminium, the ordered B2 phase, known for its stability and resistance to corrosion, appears. These striking structural differences between the nanometric and macroscopic scales once again demonstrate the unique physics that exist in the world of the infinitely small.

PhD Candidate :
Grégoire Breyton

Jury :

Dr. Christine Goyhenex – IPCMS – Referee
Pr. Claude Henry – CINaM – Referee
Dr. Pascale Bayle – CEA/Grenoble – Reviewer
Dr. Geoffroy Prévot – INSP – Reviewer
Dr. Hakim Amara – LEM – PhD co-supervisor
Pr. Christian Ricolleau – MPQ – PhD supervisor

Friday 15th December 2023 at 14h00
Pierre-Gilles de Genes Amphitheater, Paris Cité University, Paris

Impact of Mechanical Loading on Deformation and Electronic Properties of Metallic Nanoparticles


Metallic nanoparticles (NP) possess unique properties, distinct from bulk materials, offering potential application in mechanics, catalysis and optics. This thesis examines how NPs’ mechanical properties, influenced by shape, size, and composition, affect their electronic properties. Using Molecular Dynamics and Finite Element simulations, we demonstrate shape’s significant effect on the effective elastic response. Our findings highlight that plasticity is controlled by both shape and size with a universal size effect for face-centered-cubic crystalline NPs. In alloyed structures, both strengthening and softening mechanisms are observed, indicating local order’s influence on elasticity and plasticity. Finally, through tight-binding and ab initio calculations, we reveal that plastic deformation creates new reactive NP surface sites.

PhD candidate:
Matteo Erbi’


Pr. Riccardo Ferrando – University of Genoa (Italy)- Referee
Dr. Julien Godet – University of Poitiers – Referee
Pr. Francesco Montalenti – University of Milan-Bicocca (Italy) – Reviewer
Dr. Christine Mottet – CINaM – Reviewer
Dr. Fabio Pietrucci – Sorbonne University – Reviewer
Dr. Barbaru Putz- Empa (Suisse) – Reviewer
Dr. Riccardo Gatti – LEM – PhD co-supervisor
Dr. Hakim Amara – LEM – PhD supervisor

Friday 24th November 2023 at 2 pm
Contensou Room, ONERA, 29 Avenue de la Division Leclerc,92320, Chatillôn


Impact of nanostructuration on thermal conductivity in amorphous crystalline nanocomposites

Paul Desmarchelier

Johns Hopkins University, Baltimore, USA

Engineering the thermal properties of semiconductors can benefit a wide range of applications. In particular, the performance of thermal management and thermoelectric generators could be enhanced by greater control over the thermal conductivity of materials. Such a control is possible via the nanostructure, which influences phononic properties. In this context, this seminar will present several studies of amorphous/crystalline silicon nanostructures. In amorphous materials, due to disorder, the vibrational contribution to thermal conductivity is different from that of crystals, and it is possible to distinguish the propagative or ballistic contribution from the diffusive contribution. These different contributions can be studied individually, in particular using a wave-packet approach on molecular dynamics models. In a first study, this categorization is applied to nanocomposites composed of crystalline nanoinclusions in an amorphous matrix. In particular, it is shown that while it is possible to manipulate the propagative contribution via the shape and interconnection of the inclusions, the diffusive contribution is more difficult to control. In a second step, the influence of an amorphous outer layer on a crystalline nanowire is studied by combining a molecular dynamics approach and a continuous media approach. It appears that the addition of the outer layer has little effect on the flux at the amorphous-crystalline interface, but does influence the heat flux at the center of the nanowire.

How accurately can we simulate and understand the transformation mechanisms of matter ?

Fabio Pietrucci, Sorbonne Université, IMPMC, Paris


Molecular dynamics simulations can complement experiments by providing detailed, atomic- scale information about transition mechanisms between different states of materials, including nanostructures, solids, solutions, biomolecules etc. If interatomic forces are accurately described, in principle, transition states (difficult to capture in experiments due to their short lifetime) can be identified, barriers and rates can be quantitatively estimated. This kind of information can be useful to characterize the behavior of materials in real conditions of temperature and pressure, and to make sense of synthesis or degradation processes.

However, a major hurdle consists in the long characteristic timescale of many transformation processes, exceeding by far what can be simulated today (typically, from nanoseconds to microseconds). I will present some methods developed in my group, that tackle the latter challenge exploiting two strategies. The first consists in applying external forces on some flexible order parameters, specifically designed to capture and accelerate changes in the topology of the atomic network during a transformation. The second consists in directly exploring transition states and mechanisms using “transition path sampling” techniques: the resulting trajectories, projected on an order parameter, can be effectively modeled by Langevin equations, that in turn allow (based on a recently demonstrated variational principle) to optimize in a unified way the order parameter definition, the free-energy landscape and the kinetic rate. I will discuss applications to problems ranging from structural changes in core-shell nanoparticles, to crystal nucleation, to protein-protein interaction.


F. Pietrucci, Rev. Phys. 2, 32 (2017).
S. Pipolo, M. Salanne, G. Ferlat, S. Klotz, A.M. Saitta, F. Pietrucci, Phys. Rev. Lett. 119, 245701 (2017). L. Mouaffac, K. Palacio-Rodriguez, F. Pietrucci, J. Chem. Theory Comput. 19, 5701 (2023).

Synthèse par CVD de films de nitrure de bore aux propriétés optimisées pour dispositifs en optoélectronique


Dans la famille des matériaux bidimensionnels (2D), le nitrure de bore a été identifié comme un matériau stratégique. Ce semi-conducteur à grand gap (>6eV), atomiquement plan, résistant chimiquement et thermiquement, peut jouer plusieurs rôles dans les hétérostructures de matériaux 2D : substrat de graphène pour préserver la mobilité exceptionnelle de ses porteurs de charge ou couche encapsulante pour protéger d’autres matériaux 2D sensibles à leur environnement ou exalter leurs propriétés. Des démonstrateurs de principe ont été réalisés avec des monocristaux de BN. Les dimensions latérales et l’homogénéité en épaisseur du BN sont limitées par la dimension initiale millimétriques des cristaux et leur mise en oeuvre par exfoliation mécanique. Cette technique est donc difficilement industrialisable. Il est nécessaire de développer des synthèses de films de BN de dimensions, structure et qualité contrôlées pour permettre une montée en échelle. Dans cette thèse en partenariat avec la PME Annealsys, nous avons choisi de développer la synthèse de films de BN sur nickel par dépôt chimique en phase vapeur à basse pression (LPCVD). Dans un premier temps, nous avons transposé sur le bâti de l’équipementier Annealsys le procédé de synthèse de BN sur des substrats de nickel polycristallin à partir de borazine déjà maitrisé par l’équipe. Nous avons confirmé que la morphologie et la qualité du BN dépend de l’orientation cristallographique du nickel sous-jacent et que l’orientation (111) du nickel est la plus favorable pour la synthèse de film continu de BN. Nous avons donc ensuite travaillé avec des substrats monocristallins de Ni(111) /YSZ/Si(111). Nous avons porté une attention particulière à la préparation de ces substrats spécifiques et développé un traitement de stabilisation in-situ dans le bâti de dépôt, compatible avec un procédé industriel. La structure et la qualité des films de BN synthétisés, i.e. épaisseur, rugosité, séquence d’empilement, cristallinité et taille de domaines, ont été caractérisées de l’échelle atomique à l’échelle millimétrique par un panel de techniques de microscopies et spectroscopies (AFM, MEB, Raman, MET. . .). Nous avons mis en place une méthodologie de caractérisation statistique à l’échelle centimétrique, indispensable à la vérification de l’homogénéité des films de BN, prérequis pour la fabrication de dispositifs performants. Nous avons fait varier des paramètres de synthèse clés tels que la quantité de gaz précurseur ou l’épaisseur du substrat de nickel et étudié leur impact sur les films de BN. Les résultats sont discutés d’un point de vue mécanisme de croissance.


Laure Tailpied

Pr. Luc Imhoff – Université de Bourogne- Rapporteur
Dr. Laëticia MARTY – Université Grenoble Alpes – Rapporteur
Dr. Berangère Toury – Université Lyon 1 – Examinatrice
Pr. Franck Vidal – Sorbonne Université – Examinateur
Dr. Jean-Manuel Decams – Annealsys – Invité
Dr. Amandine Andrieux-Ledier – ONERA – Encadrante
Dr. Annick Loiseau – ONERA – Directrice de thèse

Mercredi 25 avril 2023 à 14h00
Salle Contensou, ONERA, 29 Avenue de la Division Leclerc,92320, Chatillôn

Cristallographie des bicouches homophases désorientées par rotation-translation

Denis Gratias et Marianne Quiquandon
CNRS-UMR 8247 IRCP, Chimie-ParisTech PSL, Paris

On se propose de discuter la symétrie résultant de la superposition de deux couches monoatomiques cristallines identiques désorientées l’une par rapport à l’autre d’une rotation-translation (α|τ).
Un réseau de coïncidence apparaît —défini par le groupe intersection des groupes de translation des réseaux des monocouches— pour un ensemble dense dénombrable de valeurs de la rotation α, qu’on discutera en toute généralité pour les quatre types de réseaux bidimensionnels, oblique, rectangle, carré et hexagonal. Ces valeurs singulières d’angle α associées aux normes σ des vecteurs unitaires du réseau de coïncidence se répartissent dans le plan (α, σ) selon des branches indexées par des suites de Farey et dont on discutera les propriétés.
Pour une rotation donnée, les symétries spatiales de ces bicouches se répartissent en un
petit nombre seulement de groupes selon la valeur de la translation τ. Ainsi les bicouches de
graphène à réseau de coïncidence ne peuvent présenter que 6 types de groupes d’espace quelles que soient la rotation a de coïncidence et la translation τ.
Dans le cas générique d’absence de réseau de coïncidence, la bicouche présente une
symétrie quasipériodique de rang 4 au plus qu’on peut décrire par une méthode de coupe à partir d’un espace de dimension 4. On montrera l’importance fondamentale du réseau-0 (0-lattice) pour décrire les symétries des figures de moiré de ces édifices.

Virtual material design

Maxime Moreaud

IFPEN, Solaize

Since 2017, IFPEN has fully entered the race for accelerated design of new materials with models creating links between synthesis and effective properties. Its AI and materials teams propose new tools for the numerical generation and characterization of materials microstructures.  
This approach realistically considers the microstructure to capture morphological and topological details at scales of interest. Numerical models link to synthesis or processing parameters, and estimate textural and usage properties. In this talk, we will discuss the general ideas of this approach, examples of multi-scale microstructures, and some recent work on numerical textural characterizations such as tortuosity and deep learning accelerated physisorption simulation.

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Rydberg atoms: a versatile tool for quantum technologies

Sylvain Schwartz

Laboratoire QTECH (ONERA)

Rydberg atoms are by definition atoms which have been excited to a state with a large principal quantum number, resulting in exaggerated properties such as a large atomic size, a long lifetime compared to other excited states and large matrix elements for the dipole operator. In practice, dipole-dipole interactions between Rydberg atoms are at the heart of quantum simulations, where they are used to create entangled atomic states. But the large dipole of Rydberg atoms can also result in a strong coupling with external electromagnetic fields, making these atoms good candidates to be used as very sensitive probes of electromagnetic environment in the GHz to THz range. I this talk, I will give a brief overview of the state of the art of quantum simulation and quantum metrology with Rydberg atoms, and present the ongoing project that we have in the QTech lab at ONERA about quantum metrology with cold Rydberg atoms trapped in optical potentials. Possible applications include electromagnetic intelligence, THz imaging and scientific applications such as the calibration of black-body shifts in state-of-the-art optical clocks (in collaboration with SYRTE and laboratoire Aimé Cotton).

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