SFP Alpes

Doru C. LUPASCU (Institute for Materials Science and CENIDE - Faculty of Engineering, University of Duisburg-Essen)
2026-02-06 10:30 - 12:30 (Europe/Paris) | ILL – Salle de Séminaire (110-111), ILL 50 71 avenue des Martyrs, Grenoble, 38042, France
Hyperfine Interactions as a Probe in Solids : The Example of a Multiferroic System : Bismuth Ferrite
Hyperfine interactions denote the coupling of the wave functions of nuclear states to the electronic shell of the atom. This coupling is a correction term to the energy of a nuclear state and equally so in reverse manner for the electronic shell of the atom.
Like nuclear magnetic resonance or Mössbaer spectroscopy, the nuclear perturbed gamma-gamma-angular correlation spectroscopy (PAC) investigates this energetic modification of the nuclear state. For sufficiently high nuclear spin value, magnetic interactions as well as quadrupole interactions become accessible. The beauty of the method is its highly local character in the crystal lattice. It directly monitors fields at a particular lattice or defect site. Similar is true for molecules.
Bismuth ferrite is a perovskite crystal exhibiting magnetic and electric ordering phenomena. It is antiferromagnetic and a very good ferroelectric. We used several probe atoms that offer suitable nuclear gamma-gamma cascades to understand these two ordering phenomena in the identical crystal and their coupling. Different from the long term belief, we proved that there is no magnetoelectric coupling in this crystal.
The presentation will introduce the measurement method, and the material system and display how it can be used to investigate solids in a very local manner.
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Hanno Filter (College 3 Secretary)
External visitors may ask for a site access to tellier(at)ill.fr
Zoom link : https://ill.zoom.us/j/98964195699?pwd=[REDACTED] – Password : [REDACTED]

William FAUGNO (LKB / Collège de France)
2026-02-06 11:00 - 12:00 | LPMMC – salle Roger Maynard (G421), CNRS - LPMMC 25 avenue des Martyrs, Grenoble, 38042, France
Quantum Many-Body Scars in the Presence of Density-Difference-Dependent Hopping
Résumé :
It has been observed that isolated quantum systems often still produce measured values consistent with thermalization. This is unexpected due to the lack of a notion of chaos or ergodicity and the unitary dynamics of the quantum theory which is at its core linear. The conditions under which we can expect isolated quantum systems to thermalize were laid out in the eigenstate thermalization hypothesis (ETH), which has generally been found to hold in a variety of systems. Still, notable violations of the ETH have been identified where a seemingly chaotic many-body quantum system exhibits some nonthermal behavior. In this talk, I will introduce the concept of quantum many-body scars (QMBS), a phenomenon in which a small subset of eigenstates violates the ETH and promote nonthermal dynamics. I will then present theoretical results on a bosonic Hamiltonian with a density-dependent hopping and describe two distinct mechanisms for scar formation that arise in this model. These mechanisms provide insight into the conditions under which QMBS can be expected to occur.
Contact : serge.florens@neel.cnrs.fr

Kei YAMAMOTO (Advanced Science Research Center, Japan)
2026-02-06 11:00 - 12:00 | CEA – Salle de Séminaire IRIG (1005 – 445), Laboratoire Irig/Spintec, salle de séminaire 445, bâtiment 1005, CEA-Grenoble, Grenoble
Spin-wave spectrum in a ferromagnetic disk
Abstract :
Angular momentum transfer in all forms contributes to the loss of information carried by dynamical spin polarisations and constitutes an important fundamental problem in spintronics. In this talk, we present a detailed microwave spectrum measurement of magnetic excitations in an Yttrium Iron Garnet disk, and how one can make sense of the multitudes of spectral lines and their magnetic field dependence theoretically. We explain how the axial symmetry of the setup leads to labelling of modes in terms of the conserved total angular momentum of the spin waves, The frequency spectrum in the saturated state is compared to analytical solutions for pure exchange as well as pure dipolar models under certain limits where different types of spectral degeneracy occur. The experimental result shows splittings of those degenerate modes, and we discuss possible interpretations in relation to angular momentum transfer between its different forms.
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More information :https://www.spintec.fr/seminar-spin-wave-spectrum-in-a-ferromagnetic-disk/​​​
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Visioconference :https://univ-grenoble-alpes-fr.zoom.us/j/98769867024?pwd=[REDACTED]​​

Isidora ARAYA DAY (DIPC San Sebastian)
2026-02-09 11:00 - 12:00 | LPMMC – salle Roger Maynard (G421), CNRS - LPMMC 25 avenue des Martyrs, Grenoble, 38042, France
Diagnosing higher order topological phases with electronic transport
Résumé :
Unlike a quantum Hall bar, a higher-order topological insulator may not have edge modes that conduct, but localized corner modes. These corner modes are robust to disorder and their appearance is diagnosed by a topological invariant that takes both onsite and spatial symmetries. In this talk, I will introduce a scattering theory for detecting higher-order topological phases only from a sample’s Fermi level properties, and will demonstrate how to apply it to different models. This theory provides an alternative approach for proving bulk–edge correspondence in intrinsic higher order topological phases, especially in presence of disorder, and it relies on the spectral flow that these phases show in the presence of magnetic flux.
Contact : serge.florens@neel.cnrs.fr

Stéphanie ROCCIA (LPSC-CNRS/UGA, Grenoble)
2026-02-10 10:30 - 11:30 | ILL – Salle de Séminaire (110-111), ILL 50 71 avenue des Martyrs, Grenoble, 38042, France
The search for neutron electric dipole moment at PSI
Résumé :
The Universe and its history are simultaneously very well understood and still a big mystery. We have amazing tools from satellites to
observatories to weight the universe over its history. But the components of the Universe can simply not yet be explained by physicists. To get the full picture, we need to identify and understand the interactions at play throughout the life of the Universe. This is the meeting point between particle physics and cosmology. At this meeting point stands the neutron, a common particle that we can uniquely use in high precision experiments.
I will present how experiments searching for a permanent electric dipole moment of the neutron (nEDM) aim at discovering new sources of CP violation beyond the Standard Model of particle physics and understanding the origin of the matter-antimatter asymmetry of the Universe. The quest for the neutron electric dipole moment started more than sixty years ago. In recent experiments, polarized ultra-cold neutrons are stored in material bottles.
I will present the ongoing efforts at the Paul Scherrer Institute in Switzerland where the n2EDM spectrometer has taken the first “physics data” in 2025. A large fraction of this dataset is dedicated to measurements of the UCN spectrum. I will present the newest UCN spectroscopy techniques that were recently published and the reasons for the importance of a deep understanding of the UCN spectrum.
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Hanno Filter (College 3 Secretary)
External visitors may ask for a site access to tellier(at)ill.fr
Zoom link : https://ill.zoom.us/j/98964195699?pwd=[REDACTED] – Password : [REDACTED]

Roxane LESTINI & Nicolas OLIVIER (Laboratoire d'Optique et Biosciences, Palaiseau)
2026-02-16 11:00 - 12:00 | LiPhy, Salle de Conférence, 140 rue de la Physique, St Martin d'Hères, 38400
Understanding DNA replication dynamics in the archaea Haloferax volcanii
Résumé :
Archaea provide a simplified yet highly informative model for deciphering the complex regulatory networks governing DNA replication and origin firing. Among them, Haloferax volcanii has a circular chromosome with four active replication origins distributed across a 3.5 Mb DNA molecule and exhibit some distinctive properties, such as a heterogeneous polyploidy, carrying 10–18 copies of its genome.
How these highly polyploid organisms regulate the activation and timing of their multiple replication origins in coordination with cell growth and division remains an open question. To address this question, we developed a multiscale approach, implementing the STORM technique in archaea for the first time, Marker Frequency Analysis by sequencing (MFA-seq) to capture the global replication profile at the population level, and fluorescence in situ hybridization (FISH) to explore ploidy variation.
Our findings reveal, with an unprecedented resolution of ~30 nm, new insights into the spatial regulation of replication foci, demonstrating their organization into clusters. We further investigated DNA replication dynamics under varying growth conditions, revealing a reduction in replication foci number that correlates with decreased replication rates and DNA content. By contrast, altering the replication initiation mode—by inactivating all four replication origins—does not disrupt the overall replication dynamics.
By integrating these techniques, we aim to characterize the replication program in H. volcanii and gain a deeper understanding of its regulation.
Contact : delphine.debarre@univ-grenoble-alpes.fr

Francesco ROSA (Politecnico di Milano, Italy)
2026-02-17 14:00 - 15:00 | CNRS – Salle Louis Weil (E424), CNRS - Institut Néel 25 avenue des Martyrs, Grenoble, 38042, France
Magnetic and orbital properties of infinite-layer nickelate and cuprate superconductors
Résumé :
Infinite-layer (IL) nickelates recently gained strong interest thanks to their apparent analogies with cuprates, including a square lattice-based structure dominated by superexchange antiferromagnetic interaction and the emergence of superconductivity upon hole doping. X-ray spectroscopies with synchrotron light are a very powerful tool for the investigation of such systems, providing complementary information to the more traditional inelastic neutron scattering. In this seminar, we discuss some of the recent results obtained by our group using both Resonant Inelastic X-ray Scattering (RIXS) and X-ray Magnetic Circular Dichroism (XMCD), mainly focusing on magnetism. RIXS results concern the analysis of dynamic spin excitations (magnons/paramagnons), investigating the effect of hole-doping on them and providing an estimate for the magnetic exchange coupling constants. Results on IL nickelates will be compared to analogous ones on cuprates, highlighting analogies and differences. XMCD analysis is devoted to the static spin order in IL nickelates, reporting the presence of a field induced out-of-plane Ni1+ spin moment. Based on magnetic field- and temperature-dependent measurements, we justify our observations with an out-of-plane canting of in-plane anti-ferromagnetically correlated Ni1+ spins, tentatively attributed to a symmetry lowering of the NiO2 planes.
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Contact : andrew.fefferman@neel.cnrs.fr

Anton POTOCNIK (IMEC, Belgium)
2026-02-17 14:00 - 15:00 | CNRS – Salle Rémy Lemaire (K223), CNRS - Institut Néel 25 avenue des Martyrs, Grenoble, 38042, France
High-coherence foundry-compatible superconducting qubit platform
Résumé :
The field of superconducting qubit technology has experienced rapid development over the past two decades. Recent advancements in the fabrication, control and measurement of superconducting quantum devices have enabled integration of hundreds of qubits on a single chip. However, the path towards larger-scale integration of thousands of qubits on a chip remains unclear. This talk presents imec’s platform for scalable superconducting qubit fabrication, which is based on foundry-compatible thin film processing 1 and overlay Josephson-junction fabrication 2. The platform enables all-optical superconducting transmon qubit fabrication on 300 mm wafers, achieving near state-of-the-art coherence times, record-low aging and comparable Josephson junction variability to standard shadow-evaporation technique 3. A key focus of this presentation will be the understanding and mitigation of microwave losses induced by various fabricaiton steps such as Ar-milling 4 and oxide removal 6,7 and materials such as -Ta 5 or ultra-high-resistivity silicon. The talk will conclude with an outline of ongoing efforts toward large-scale qubit characterization and control using cryo-CMOS electronics operating near qubits at the mixing-chamber plate of a dilution refrigerator 8.
1 Mongillo, et al., IEDM (2022).
2 Verjauw et al., npj Quantum Information 8, 93 (2022).
3 Van Damme, et al., Nature, 634, 74 (2024).
4 Van Damme, et al., PRA 20, 014034 (2023).
5 Lozano, et al. Mater. Quantum. Technol. 4, 025801 (2024).
6 Verjauw, et al., PRA 16, 014018 (2021).
7 Lozano, et al., Advanced Science 12, e09244 (2025).
8 Acharya, et al., Nature Electronics, 6, 900 (2023).
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Contact : equipe-seminaires-nano@listes.grenoble.cnrs.fr

Igor ROZHANSKIY (National Graphene Institute, University of Manchester)
2026-02-17 14:00 - 15:00 | CEA – Salle de Séminaire IRIG (1005 – 445), Laboratoire Irig/Spintec, salle de séminaire 445, bâtiment 1005, CEA-Grenoble, Grenoble
Interacting spin physics in 2D : flat bands, SOC renormalization, and chiral textures
Résumé :
Two-dimensional materials and their heterostructures offer a controllable setting where exchange, spin-orbit coupling (SOC), and electron interactions shape the spin-resolved electronic structure and response. This seminar links two recent directions of my work through this common theme.
The first part focuses on van der Waals magnets (chromium trihalides) combined with graphene. Narrow, spin-polarized conduction bands make these systems susceptible to charge-transfer-driven doping and strong correlations. Using DFT-calibrated effective tight-binding models, I will show how flat-band features and longer-range hopping processes determine the low-energy spectrum and favor regimes with heavy, strongly interacting carriers.
​ The second part addresses many-body renormalization of SOC in monolayer transition metal dichalcogenides. Exchange effects can enhance the conduction-band spin-orbit splitting in a density-dependent manner. I will outline ​the underlying mechanism and discuss how it can be inferred from gated transport and quantum-oscillation measurements, including multilayer configurations where valley structure and interlayer coupling provide additional diagnostics.
A short outlook will touch on chiral spin textures, such as skyrmions, and how real-space chirality can contribute to transverse signals, emphasizing possible connections and open questions for 2D material platforms.
https://www.cea.fr/drf/irig/Pages/Animation-scientifique/seminaires/2026_Rozhanskiy.aspx
Contact : admin.spintec@cea.fr

Dmitri KHVESHCHENKO (University of North Carolina)
2026-02-20 11:00 - 12:00 | LPMMC, CNRS - Bat G, salle Roger Maynard G-421, Grenoble
Applied Hall-o-graphy with no strings attached
Résumé :
This discussion aims at ascertaining the true status of the so-called applied-holographic approach to strongly correlated quantum matter. The latter ranges from ‘not even wrong’ for the constructions based on the ad hoc ‘AdS/CMT’ to ‘might be right, albeit for the wrong reason’ for those emerging in the context of phase-space bosonization and the related ‘Hall-o-graphic’ hydrodynamics.The presentation will be made accessible to the wide audience of non-experts and students.
Contact : serge.florens@neel.cnrs.fr
