Correlation between non-Fermi-liquid behavior and superconductivity in (Ca, La)(Fe,Co)As2 iron arsenides: A high-pressure study

TL;DR

This study reveals that in Ca1-xLaxFe1-yCoyAs2 superconductors, increasing pressure induces a transition from non-Fermi-liquid to Fermi-liquid behavior, correlating with suppressed superconductivity and Hall coefficient extremum, highlighting the role of spin fluctuations.

Contribution

It provides systematic evidence linking NFL behavior, multigap superconductivity, and Hall coefficient anomalies to spin fluctuations in 112-type iron arsenide superconductors under pressure.

Findings

Pressure induces NFL to FL crossover in resistivity.

Superconducting transition temperature Tc decreases with pressure.

Hall coefficient extremum diminishes as NFL behavior weakens.

Abstract

Non-Fermi-liquid (NFL) phenomena associated with correlation effects have been widely observed in the phase diagrams of unconventional superconducting families. Exploration of the correlation between the normal state NFL, regardless of its microscopic origins, and the superconductivity has been argued as a key to unveiling the mystery of the high-Tc pairing mechanism. Here we systematically investigate the pressure-dependent in-plane resistivity and Hall coefficient (RH ) of a high-quality 112-type Fe-based superconductor Ca1-xLaxFe1-yCoyAs2 (x = 0.2,y = 0.02). With increasing pressure, the normal-state resistivity of the studied sample exhibits a pronounced crossover from non-Fermi-liquid to Fermi-liquid behaviors. Accompanied with this crossover, Tc is gradually suppressed. In parallel, the extremum in the Hall coefficient RH (T ) curve, possibly due to anisotropic scattering induced by spin fluctuations, is also gradually suppressed. The symbiosis of NFL and superconductivity implies that these two phenomena are intimately related. Further study on the pressure-dependent upper critical field reveals that the two-band effects are also gradually weakened with increasing pressure and reduced to the one-band Werthamer-Helfand-Hohenberg limit in the low-Tc regime. Overall, our paper supports the picture that NFL, multigap, and extreme RH (T ) are all of the same magnetic origin, i.e., the spin fluctuations in the 112 iron arsenide superconductors.