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• 06 juillet
  [Institut Quantique] Rencontre de groupe IQ : David Sénéchal
  06 juillet

  [Institut Quantique] Rencontre de groupe IQ : David Sénéchal

  Lieu : D4-2020 Description : Suite de l'introduction à la théorie des groupes et à ses applications à la supraconductivité.

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• 14 juillet
  [Institut Quantique] Séminaire IQ – Marcello Civelli
  14 juillet

  [Institut Quantique] Séminaire IQ – Marcello Civelli

  Lieu : Auditorium de l'IQ Description : Lieu : Auditorium de l'IQRejoindre la réunion Microsoft Teams / Join the Microsoft Teams meetingMarcello CivelliLaboratoire de physique des solides, ParisInvité d'André-Marie TremblayRésumé/AbstractÀ venirTitre/TitleÀ venir

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• 26 juillet
  [Institut Quantique] Projets-porteurs : Bastien Michon
  26 juillet

  [Institut Quantique] Projets-porteurs : Bastien Michon

  Lieu : Auditorium de l'IQ Description : Rencontre de suivi des projets porteurs sur la matière ultra-quantique (IQuprates) et sur les excitations émergentes dans les matériaux quantiques. Où : Auditorium de l'IQQuand : Chaque mardi 15h30 Bastien MichonInvité de Louis Taillefer Titre/TitleAn infrared optical study across the pseudogap critical point of cuprates: quantum criticality, scaling laws and link to superconductivity Résumé/AbstractThe nature of the pseudogap state in the phase diagram of cuprates has remained an enigma since their discovery in 1986. New experimental breakthroughs have recently revealed important signatures at the pseudogap critical point p*, where the pseudogap state vanishes in doping at zero temperature:1)     Transport measurements put in evidence a dramatic drop in the carrier density n – from 1+p to p – caused by a Fermi-surface reconstruction inside the pseudogap state [1-3].2)     Normal state specific heat shows a strong effective mass m* enhancement and an unusual logarithmic divergence in temperature at p*, resulting from a quantum critical point localized at p* [4][5].Quantum criticality was already suspected in holedoped cuprates by a linear resistivity ρ∝ T [6] and power law dependence in the infrared optical conductivity σ(ω,T) ∝ ω-ν [7], with ωthe photon energy and ν the critical exponent. However, the critical exponents observed in optics ν < 1 seem to be in direct contradiction with the linear in temperature resistivity and logarithmic specific heat related to an exponent ν= 1.In this work, we study the pseudogap critical point p* with low temperature infrared spectroscopy in La2-xSrxCuO4 and La1.8-xEu0.2SrxCuO4cuprates. Through the extended Drude model on σ(ω,T), we extract the spectral weight K, the optical scattering rate τ(ω,T) and effective mass ratio m*/m(ω,T)at different doping contents across p*. With a theoretical model, we are able to compare three experimental probes: resistivity, specific heat and infrared spectroscopy by using only few parameters such as the critical exponent ν. In particular, we can describe the experimental data within reasonable error bars and explain the apparent contradictions between these three probes [8]. In addition, the study of the spectral weight K in a function of doping content confirms the aforementioned behaviors concerning the carrier density n and the effective mass m* across p*, and reveals an intriguing linear relation between the spectral weight associated to the electronic correlations and the superconducting critical temperature Tc [9]. [1]S. Badoux, W. Tabis, F. Laliberté et al., Nature 531, 210 (2016).[2]C. Collignon, S. Badoux, S.A.A. Afshar, B. Michon et al., Phys. Rev. B 95, 224517 (2017).[3]B. Michon, A. Ataei, P. Bourgeois-Hope et al., Phys. Rev. X 8, 041010 (2018).[4]B. Michon, C. Girod, S. Badoux et al., Nature 567, 218 (2019).[5]C. Girod, D. LeBœuf, A. Demuer et al., Phys. Rev. B 103, 214506 (2021).[6]R.A. Cooper, Y. Wang, B. Vignolle et al., Science 323, 603 (2009).[7]D. van der Marel, H.J.A. Molegraaf, J. Zaanen et al., Nature 425, 271 (2003).[8]B. Michon, C. Berthod, C.W. Rischau et al., arXiv:2205.04030 (2022).[9]B. Michon, A.B. Kuzmenko, M.K. Tran et al., Phys. Rev. R 3, 043125(2021).

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