Thermoelectricity evidence for quantum criticality in clean infinite-layer nickelate films

TL;DR

This study provides evidence of quantum criticality in clean infinite-layer nickelate films through thermoelectric measurements, revealing a disorder-driven transition and antiferromagnetic correlations similar to cuprates, with implications for superconductivity.

Contribution

It demonstrates the presence of quantum criticality and antiferromagnetic correlations in nickelate films, highlighting their similarity to cuprates and advancing understanding of their superconducting mechanisms.

Findings

Disordered films show flat $S/T$ behavior.

Cleaner films exhibit logarithmic divergence in $S/T$.

Quantum criticality persists across a wide doping range.

Abstract

We investigate the Seebeck coefficient ($S$) in infinite-layer nickelate films with different disorder levels. The disordered NdNiO$_{2}$ film exhibits a flat $S/T$ curve, whereas cleaner samples display a logarithmic divergence with decreasing temperature, followed by a pronounced ``hump'' near 25 K. These distinct behaviors reveal a disorder-driven transition from band-structure-dominated transport to quantum-critical-dominated transport. Below the ``hump'' temperature, four-fold symmetry breaking is observed in the in-plane angular magnetoresistance, indicating the presence of short-range antiferromagnetic order in parent infinite-layer nickelate films. Furthermore, the logarithmic divergence in $S/T$ is also observed in a clean superconducting Sm$_{0.73}$Ca$_{0.05}$Eu$_{0.22}$NiO$_{2}$ film, where it coexists with linear-in-temperature resistivity over the same temperature range. These findings demonstrate the existence of quantum criticality over a wide doping range in clean infinite-layer nickelate films, similar to cuprates, which highlights the central role of antiferromagnetic spin correlations in their superconducting pairing mechanisms.