Le Centre de Physique Théorique (CPHT) réunit des chercheurs dont les activités couvrent un large spectre de la Physique, tant dans ses aspects fondamentaux qu'appliqués.
Le CPHT est une unité mixte de recherche (UMR 7644) du Centre National de la Recherche Scientifique (CNRS) et de l’Ecole polytechnique. Au niveau du CNRS, il est rattaché à l’Institut de physique. Le CPHT a également un partenariat avec le Collège de France.
Le CPHT, dirigé par Jean-René Chazottes, directeur de Recherche au CNRS, est implanté sur le campus de l’Ecole Polytechnique à Palaiseau, dans le bâtiment 6 et dans l'aile 0 du bâtiment 5. Le secrétariat se situe dans le Bâtiment 6, bureaux 06.1046 et 06.1045. 
 

Adresse postale : 
CPHT 
Ecole Polytechnique 
91128 Palaiseau cedex 
France

Tél. Secrétariat : 01 69 33 42 01

Pour écrire un email à un membre du laboratoire : prenom.nom@polytechnique.edu

 

séminaire conjoint LSI+CPHT+PMC = M4S

Séminaire conjoint LSI+CPHT+PMC = M4S

vendredi 19 septembre à 10h

nouvelle salle de séminaire du PMC (anciennement salle Jean Mandel, au RDC de l'aile 5, près de l'aile 3).

Ioan Pop
(Karlsruhe Institute of Technology)

"Superconducting qubits and amplifiers resilient to tesla-scale magnetic fields"

Superconducting qubits with quantum non-demolition readout and active feedback can act as information engines to probe and control microscopic degrees of freedom, both engineered and environmental. However, the magnetic field bias poses a significant challenge for the operation of conventional qubits. We demonstrate a fluxonium qubit with a granular aluminum nanojunction (gralmonium) that maintains spectral stability and coherence above 1 T [arxiv.org/abs/2501.03661]. This robust performance enables exploration of spin environment dynamics and supports hybrid quantum architectures integrating superconducting qubits with spin systems.

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SUCCESS-2025, Les Houches 15-26 september 2025

 

Doctoral Training: SUCCESS-2025 - School on Ultraviolet and X-Ray Spectroscopies of Correlated and Topological Electron Systems

15 - 26 september 2025

Les Houches

Strong electron correlations and topology lie at the heart of quantum materials and their exotic states of matter. These are best understood by studying their electronic structure. This school, addressed to PhD students and young researchers, will introduce the recent experimental and theoretical developments in UV and X-ray spectroscopies, from their basic principles to their applications in the study of correlated materials.

The organizers:
Andrés F. Santander-Syro – Université Paris-Saclay (Orsay, France)
Silke Biermann – Institut Polytechnique de Paris (Palaiseau, France)
Patrick Le Fèvre – Université de Rennes (Rennes, France)
Ralph Claessen – Universität Würzburg (Germany)

More information can be found on the session's website.

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Séminaire des jeunes chercheurs du CPHT

 

Le séminaire des jeunes chercheurs du CPHT aura lieu le lundi 30 juin 2025 à 15h00 à la Salle de conférence Louis Michel avec deux présentations :

Valentine Maris from ENS de Lyon Introduction to noncommutative geometry and deformed Minkowski space-time :
Noncommutative geometry provides a representation of space-time in terms of associative algebras of operators. The final goal is to end up with a "quantum space-time" which should encode quantum gravity effects at an effective level. Recently, construction of such quantum space-times has been investigated and led to deformations of the usual Minkowski space-time.

Thomas Pochart QFT in AdS and its flat-space limit :
The Anti-de Sitter space is a fundamental concept in physics, arising naturally in GR and playing a key role in holography. We will discuss recent advances in quantum field theory for AdS spaces, and in particular its large radius limit, in which it is expected that we efficiently recover flat-space quantities.

Le séminaire sera suivi d'un goûter.

Français

Seminar announcement

Monday 30th June at 11:00am – Seminar Room Louis Michel at CPHT, Ecole Polytechnique
 
Title: Topological superconductivity and charge order in Sn/Si(111)
 
Stephan Rachel, University of Melbourne Australia
 
Abstract:
In this talk, I will discuss competing many-body states on the triangular lattice. Motivated by the recently discovered superconductivity in boron-doped Sn/Si(111) with a Tc as high as 10K [1], I will focus on unconventional superconductivity of correlated electrons on the triangular lattice. I will further demonstrate the significance of Rashba spin-orbit couling for materials such as Sn/Si(111) and show that the superconducting phase possesses a surprisingly rich Chern-number landscape [2]. I will discuss the implications of our findings for Sn/Si(111), compare observables and also emphasize the significance of related compounds such as Pb/Si(111) and Sn/SiC(0001) [3].
 
[1] F. Ming, X. Wu, C. Chen, K. D. Wang, P. Mai, T. A. Maier, J. Strockoz, J. W. F. Venderbos, C. Gonzalez, J. Ortega, S. Johnston, and H. H. Weitering, Nat. Phys. 19, 500 (2023).
[2] M. Bunney, J. Beyer, R. Thomale, C. Honerkamp, S. Rachel, Phys. Rev. B Letters 110, L161103 (2024).
[3] L. Marchetti, M. Bunney, D. Di Sante, S. Rachel, Phys. Rev. B 111, 125115 (2024).
 
Join Zoom Meeting
Meeting ID: 937 3477 1384
Passcode: 313476
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Seminar announcement

Friday 27th June at 14:00pm – Seminar Room Louis Michel at CPHT, Ecole Polytechnique
 
Topological devil's step in a constrained kagome Ising antiferromagnet
 
Jeanne Colbois, CNRS and Institut Louis Neel, Grenoble
 
Despite their apparent simplicity, classical Ising models can give rise to exotic ground state phases in the presence of frustration (e.g., when antiferromagnetic pair interactions cannot be simultaneously minimized) [1]. The finite-temperature physics induced by such  macroscopically degenerate ground states can prove extremely rich, but, except at fine-tuned point, studying them with numerical or analytical methods can prove difficult. 
 
I will briefly describe how tensor network methods -- well known for their success in  the study of quantum spin systems -- can also help solve such classical statistical mechanics problems on a lattice [2,3]. As a case in point, I will discuss a surprising staircase behavior observed in the constrained limit of a farther-neighbor kagome Ising antiferromagnet. After recalling some key notions, I will argue that, unlike in standard Devil's staircases, the driving mechanism here is Kastelyn-like and leads to a staircase of topological origin [4].
 
[1] C. Lacroix, P. Mendels, and F. Mila, Introduction to Frustrated Magnetism: Materials, Experiments, Theory (2011)
[2] B. Vanhecke, J. Colbois et al, Solving Frustrated Ising models using tensor networks, Phys. Rev. Res, (2021)
[3] J. Colbois, B. Vanhecke et al, Partial lifting of degeneracy in the J1-J2-J3 Ising antiferromagnet on the kagome lattice, Phys. Rev. B (2022)
[4] A. Rufino, S. Nyckees, J. Colbois, and F. Mila, Topological devil's staircase in a constrained kagome Ising antiferromagnet, arXiv:2505.05899
 
 
Join Zoom Meeting
Meeting ID: 939 9582 7714
Passcode: 697603
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Séminaire des jeunes chercheurs du CPHT

 

Le séminaire des jeunes chercheurs du CPHT aura lieu le vendredi 13 juin 2025 à 14h00 à la Salle de conférence Louis Michel avec deux présentations :

Fanny Eustachon  CFT in higher dimensions for dummies

Francesco Cassol Interplay of Spin-orbit coupling, Coulomb interaction and magnetism in iridate materials: the example of Ba2IrO4 and Sr2IrO4

Le séminaire sera suivi d'un goûter.

Français

séminaire conjoint LSI+CPHT+PMC = M4S

Séminaire conjoint LSI+CPHT+PMC = M4S

Mardi 27 mai 11h00

Salle de conférence Louis Michel (CPHT)

Benoît Fauqué
(Chargé de Recherche CNRS, LPEM, ESPCI (Paris))

Ferroelectric fluctuations shape the superconducting dome of SrTiO₃

Superconducting domes, ubiquitous across a variety of quantum materials, are often understood as a favored window for pairing, opened by fluctuations of competing orders that induce a peak in the doping evolution of the superconducting transition temperature. Yet, a quantitative understanding of how such a window closes remains lacking. In this talk, I will discuss the case of the superconducting dome in doped SrTiO₃. In contrast to other families, the parent compound is not magnetic but instead is a quantum paraelectric, characterized by a large dielectric constant (ε ≈ 20,000). I will show that its superconducting dome arises from the interplay between the increase in the density of states and the inevitable collapse of the quantum paraelectric phase—both induced by doping. I will also discuss the remarkable transport properties, such as a linear, quasi-isotropic magnetoresistance, which we observe as the quantum paraelectric phase dies off.

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