Antoine Georges, Gabriel Kotliar and Dieter Vollhardt have been jointly awarded the 2022 Feenberg Memorial Medal for established work that has significantly advanced the field of many-body physics. The award is for the Dynamical Mean Field Theory (DMFT) method, now an important tool in the Many-Body community. The award is for the Dynamical Mean Field Theory (DMFT) method, now an important tool in the Many-Body community.
See: https://tarheels.live/rpmbt21/2022/08/05/feenberg-memorial-medal-awardees-announced/

Julian Legendre will publicly defend his thesis work on September 15, 2022 at 10:00 a.m. at the CPHT in the Louis Michel conference room

Title: Topological phases, light response and kagome lattice

Advisor: Karyn Le Hur

Jury :

Walter Hofstetter (Président du Jury) Professeur, Goethe Universität Frankfurt (Institut für Theoretische Physik)
Grégoire Misguich (Rapporteur) Chercheur en physique théorique et ingénieur CEA (Institut de Physique Théorique)
Guillaume Roux (Rapporteur) Maître de Conférences, Université Paris-Saclay (Laboratoire de Physique Théorique et Modèles Statistiques)
Pierre Pujol (Examinateur) Professeur, Université Paul Sabatier Toulouse (Laboratoire de Physique Théorique)
Ulrich Schneider (Examinateur) Profeseur, University of Cambridge (Cavendish Laboratory)
Karyn Le Hur (Directrice de thèse) Directrice de Recherche au CNRS et Professeure PCC, École Polytechnique (Centre de Physique Théorique)

Abstract: We theoretically study topological lattice models relevant to current experimental solid- state and artificial systems. We develop an explicit analytical computation of the Chern number in the systems we study and we compare it with other computation methods of this topological invariant. We propose a protocol, based on the local response to a light input, to probe the topological properties of a Haldane boson model in a photonic system. On the kagome lattice, we investigate (i) a magnetic and topological phase transition for a two-channel model, in relation with recently discovered quantum materials, and (ii) a time- reversal topological model with flux, Rashba spin-orbit coupling and Hubbard interactions, relevant for realization in cold-atom gases.

After the reception, we planned a seminar on Condensed matter and Topology

The 5th CPHT Young Researchers Seminar will be held on June 16, 2022 at 3:00 p.m. in the Louis Michel Conference Room with two presentations given by :

Matthieu Vilatte : Holography fluid/gravity and its flat space extension

Ephraim Bernhardt : Topology of a driven spin-1/2

The seminar will be followed by a high tea.

Mufei Luo soutiendra publiquement ses travaux de thèse le 9 septembre 2022 à l'Université Joao Tong de Shanghai (en chinois)
pour conclure son travail de thèse intitulé “The role of laser bandwidth and random phase effects on the coupling of stimulated scatter in inhomogeneous plasmas”, directeurs de thèse Stefan Hüller (CPHT), Min Chen (Shanghai Joao Tong Univ.), Zhengming Sheng (Shanghai Joao Tong Univ. et Strathclyde)

Sabine Harribey soutiendra publiquement ses travaux de thèse le 17 juin 2022 à l'INRIA (bâtiment Alan Turing), salle Gilles Kahn.

Titre de la thèse : Renormalization in tensor field theory and the melonic fixed point

Participer à la réunion Zoom pour la soutenance de thèse :
https://ecolepolytechnique.zoom.us/j/89946552020
ID de réunion : 899 4655 2020

Co-directeurs de thèse : Razvan Gurau, Dario Benedetti et Christoph Kopper

Membres du jury :
- Holger Gies (Université Friedrich-Schiller de Jena) Rapporteur
- Grigory Tarnopolsky (Carnegie Mellon University) Rapporteur
- Matthias Bartelmann (Université d’Heidelberg)
- Lauriane Chomaz (Université d’Heidelberg)
- Vincent Rivasseau (Université Paris-Saclay)

Abstract: This thesis focuses on the study of the renormalization group flow in tensor field theories. Its first part considers a quartic tensor model with O(N)^3 symmetry and long-range propagator. The existence of a non-perturbative fixed point in any d at large N is established. We found four lines of fixed points parametrized by the so-called tetrahedral coupling. One of them is infrared attractive, strongly interacting and gives rise to a new kind of conformal field theories, called melonic CFTs. This melonic CFT is then studied in more details. We first compute dimensions of bilinears and operator product expansion coefficients at the fixed point. The results are consistent with a unitary CFT at large N. We then compute 1/N corrections to the fixed point. At next-to-leading order, the line of fixed points collapses to one fixed point. However, the corrections are complex and unitarity is broken at next-to-leading order. Finally, the F-theorem is investigated for this model. This theorem states that the free energy of a CFT on the sphere in dimension 3 decreases along the renormalization group flow. We show that our model respects this theorem. The next part of the thesis investigates sextic tensor field theories in rank 3 and 5. In rank 3, we found two infrared stable real fixed points in short range and a line of infrared stable real fixed points in long range. Surprisingly, the only fixed point in rank 5 is the Gaussian one. For the rank 3 model, in the short-range case, we still find two infrared stable fixed points at next-to-leading order. However, in the long-range case, the corrections to the fixed points are non-perturbative and hence unreliable: we found no precursor of the large N fixed point.  The last part of the thesis investigates the class of model exhibiting a melonic large N limit. Indeed, this limit was lacking for models with ordinary tensor representations of O(N) and Sp(N), such as symmetric traceless or antisymmetric ones. Recently, it was proven that models with tensors in an irreducible representation of O(N) or Sp(N) in rank 3 indeed admit a large N limit. This proof is here extended in rank 5. This generalization relies on recursive bounds derived from a detailed combinatorial analysis of Feynman graphs involved in the perturbative expansion of our model.

La soutenance d’habilitation à diriger des recherches de Blaise Goutéraux sur le sujet : « Holography, hydrodynamics and strongly-correlated condensed matter » aura lieu le 9 juin 2022 à 15h00 au CPHT (Salle Louis Michel).

Participer à la réunion Zoom : https://ecolepolytechnique.zoom.us/j/89894053078?pwd=cFExWTBqbjUwQWllU3p...

Mini-conference on Condensed Matter, Fields and Gravity

June 10th, 2022 10:00 am - 15:30 pm

at CPHT, room Louis Michel, CPHT, Ecole Polytechnique

Schedule and speakers :

10am-10:45am: Costas Bachas (LPTENS, Paris, France)

10:45am-11:15am: Coffee break

11:15am:12pm: Chris Herzog (King's College, London, UK)

12pm-12:45pm: Kristan Jensen (University of Victoria, Canada)

12:45pm-2pm: Lunch

2pm:2:45pm: Karl Landsteiner (UAM, Madrid, Spain)

2:45pm-3:30pm: Jan Zaanen (Leiden University, the Netherlands)

3:30pm: Coffee break

4:00pm-4:45pm: Ayan Mukhopadhyay (IIT Madras, India)

Titles and Abstracts

Organized by Blaise Goutéraux (CPHT)

La soutenance d’habilitation à diriger des recherches d'Alaska Subedi
sur le sujet : « Structure property relationships in complex materials »
aura lieu le 18 mai 2022 à 14h00 au CPHT (Salle Louis Michel)

Mini-workshop  "Strange Metals, SYK Models and Beyond",  June 2-3, 2022, Collège de France, Paris