2025/10/14 by C. Iorio-Duval, Iorio-Duval, C., E. Beauchesne-Blanchet +18 · 1 citation
Engineering · Materials Science · Physics and Astronomy · #Advanced Materials Characterization Techniques #Metallurgical and Alloy Processes #Rare-earth and actinide compounds #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.2510.12786
openalex publication_date 2025/10/14 · openalex created_date 2025/10/17 · openalex updated_date 2026/07/28
The quantum-critical origin of strange metals remains debated, particularly in cuprates where T-linear resistivity emerges at the end of the pseudogap phase, a regime without long-range order whose nature remains one of the largest mysteries of quantum materials~\citeMichon2019Thermodynamic, zhong2022. Superconducting infinite-layer nickelates provide a new platform to revisit this issue, given their close similarities to cuprates. Here too, T-linear resistivity onsets at a critical doping x^⋆ near the middle of the superconducting dome. Establishing whether x^⋆ is a quantum critical point (QCP) -- a zero-temperature phase transition -- typically relies on the electronic specific heat C\rm el, which follows C\rm el/T ∝ log(T) at a QCP, rather than the constant behaviour of a conventional metal. However, the thin-film form of infinite-layer nickelates precludes calorimetry. We therefore use the Seebeck coefficient as a low-temperature proxy for specific heat per carrier. In La\rm 1-xSr\rm xNiO2 at x^⋆, the high-temperature Seebeck response is quantitatively captured by the ARPES-measured band structure, indicating well-defined quasiparticles. Below 60 kelvin, however, S/T develops a logarithmic divergence, S/T ∝ log(T), persisting to the lowest temperature once superconductivity is suppressed by B=41.5~T. This identifies x^⋆ as a QCP terminating the underdoped phase. Finally, we find that the carrier density n\rm d of the Ni-d\rm x2-y2 pocket drops from 1+x above x^⋆ to x below, mirroring the hallmark of the pseudogap phase in cuprates and iridates. These results point to a pseudogap-like underdoped regime ending at x^⋆, from which strange-metal behaviour emerges.