Séminaire QuantAlps : mardi 20 janvier 2026 à 15h00
Gaël Grissonnanche (LSI, Ecole Polytechnique)
Titre : Quantum criticality in superconducting nickelates
Institut Néel, Salle E424 (Salle Louis Weil)
Résumé : Quantum criticality appears to be a common feature of strange metals that migt lead to the emergence of superconductivity. Signatures of quantum criticality in cuprate superconductors have been debated for decades. Reports of thermodynamic divergence in the specific heat [1], a drop in carrier density measured by the Hall effect [2], evidence of Fermi surface reconstruction from angle-dependent magnetoresistance (ADMR) [3], and the presence of a strange metal phase have fueled the long-standing discussion. Yet, consensus on the existence or role of a quantum critical point in cuprates remains elusive.
Superconducting infinite-layer nickelates offer an opportunity to explore whether quantum criticality is a unifying feature of both cuprates and nickelates. Nickelates share many characteristics with cuprates, including nodal superconductivity [4], a strange metal regime [5], and a sudden change in the Hall effect as a function of doping [5]. Nevertheless, because these materials only grow as thin films, standard specific heat and ADMR experiments cannot be performed, and thermodynamic signatures and evidence of Fermi surface transformations associated with a quantum critical point remain elusive.
We have conducted Seebeck effect experiments as a proxy for the specific heat to probe quantum criticality in these materials. We find a quantum critical point at the onset of the strange metal regime and at the end of an underdoped phase apparent to the pseudogap phase of cuprates [6].
This result further supports quantum criticality as a common feature of strongly correlated superconductors.
References
[1] Michon et al. Nature 567, 218 (2019)
[2] Badoux et al. Nature 531, 210 (2016)
[3] Fang et al. Nature Physics 18, 558 (2022)
[4] Ranna et al. PRL 135, 126501 (2025)
[5] Lee et al. Nature 619, 288 (2023)
[6] Iorio-Duval et al. arXiv:2510.12786
