The center for Theoretical Physics (CPHT) at Ecole Polytechnique gathers research scientists working in diverse domains of fundamental and applied Physics. The overall coherence is assured by the corpus of common, transposable, mathematical and numerical methods.
CPHT is a joint research unit of CNRS and Ecole Polytechnique, and has a partnership with the Collège de France. His director is Jean-René Chazottes, Senior Researcher at CNRS.
CPHT is on the campus of Ecole Polytechnique, buildings 5 and 6. The reception offices are located in building 6 , offices 06.1046 and 06.1045.
 

Postal Address :
CPHT 
Ecole Polytechnique 
91128 Palaiseau cedex 
France

Secretary phone number : 01 69 33 42 01 (from abroad: +33 169 334 201)

Write an email to someone at CPHT :  : firstname.lastname@polytechnique.edu

 

CPHT Young Researcher Seminar

 

The CPHT Young Researchers Seminar will be held on Monday the 30th of June at 3:00 PM  in room Louis Michel :

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.

The seminar will be followed by a high tea.

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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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CPHT Young Researcher Seminar

 

The CPHT Young Researchers Seminar will be held on Friday the 13th of June at 2:00 PM  in room Louis Michel :

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

The seminar will be followed by a high tea.

English

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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Prix des meilleures thèses décernées par l'IPP

L'IPP a reçu 68 candidatures pour le prix IP Paris de la meilleure thèse 2025, dont beaucoup étaient d'une qualité exceptionnelle. Après une longue et difficile délibération, le comité des prix de thèse a décidé d'attribuer 2 prix de la meilleure thèse de l'IP Paris (ex-aequo) et 7 prix de la meilleure thèse de doctorat du département.

Parmi eux, Matthieu Vilatte a reçu le prix de la meilleure thèse de doctorat du département de physique pour son travail intitulé : "Adventures in (thermal) Wonderland : Aspects of Carrollian physics, asymptotically flat spacetimes and thermal field theory ». Cette thèse a été encadrée conjointement par Tasos Petkou (Université Aristote de Thessalonique, Grèce) et Marios Petropoulos (Centre de Physique Théorique, École polytechnique).

Les résultats seront officiellement annoncés

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La seconde révolution quantique dans les laboratoires de l’X

 

Quantum, highlighted in this year 2025, is one of the major research field at the Center for Theoretical Physics. The researchers of the laboratory develop a variety of activities around quantum materials, quantum simulation, quantum computing, and quantum machine learning, among others. An overview of this 'second quantum revolution' with Laurent Sanchez-Palencia, head of the Quantum Matter team at CPHT, in an article published on the École Polytechnique website.

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