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Real-time detection of critical slowing down in ultrafast quenches of superconductivity

Guillermo Nava Antonio1, Théo Courtois2, Corentin Pfaff2, KM Shivangi Shukla1, Asle Sudbø3, Stéphane Mangin2,4, Thomas Hauet2, and Chiara Ciccarelli1,3,*

  • *Contact author: cc538@cam.ac.uk
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Phys. Rev. B 114, 014505 – Published 7 July, 2026

DOI: https://doi.org/10.1103/pz3y-1447

Abstract

We employ optical pump-THz probe spectroscopy to chart the ultrafast superconductivity suppression in NbN over a broad range of excitation fluences. Our measurements uncover a pronounced lengthening of the superconductivity quenching time when the absorbed optical energy is close to the condensation energy of the superconductor, which constitutes a nonequilibrium analog of critical slowing down on a timescale comparable to that of superconducting fluctuations. Time-dependent Ginzburg-Landau simulations reproduce this behavior and ascribe it to the flattening of the free-energy landscape at the dynamical phase-transition boundary. Our findings represent a direct observation in real time of slowed-down superconductivity dynamics in proximity to a critical point and open a pathway for investigating out-of-equilibrium critical phenomena with time-resolved THz spectroscopy.

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Phys. Rev. B 114, 014505– Published 7 July, 2026
  • Received 1 December 2025
  • Revised 27 March 2026
  • Accepted 15 June 2026
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