Real-time detection of critical slowing-down at the superconducting phase transition

Guillermo Nava Antonio; Théo Courtois; Corentin Pfaff; KM Shivangi Shukla; Asle Sudbø; Stéphane Mangin; Thomas Hauet; Chiara Ciccarelli

arXiv · 2603.12473

Real-time detection of critical slowing-down at the superconducting phase transition

Guillermo Nava Antonio·Théo Courtois·Corentin Pfaff·KM Shivangi Shukla·Asle Sudbø·Stéphane Mangin·Thomas Hauet·Chiara Ciccarelli

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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 non-equilibrium 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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Guillermo Nava Antonio, Théo Courtois, Corentin Pfaff, KM Shivangi Shukla, Asle Sudbø, Stéphane Mangin, Thomas Hauet, Chiara Ciccarelli. 2026-03-12. Real-time detection of critical slowing-down at the superconducting phase transition. https://arxiv.org/abs/2603.12473

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