A crossover in phase diagram of NaFe$_{1-x}$Co$_x$As determined by electronic transport measurements

TL;DR

This study investigates electronic transport in NaFe$_{1-x}$Co$_x$As, revealing a crossover in Hall angle behavior and a pseudogap-like phase transition, advancing understanding of superconductivity and electronic phases in ferropnictides.

Contribution

It identifies a doping-dependent crossover in Hall angle behavior and pseudogap-like phase in NaFe$_{1-x}$Co$_x$As, linking transport properties to phase diagram features.

Findings

Cotangent of Hall angle follows $T^4$ in parent compound.

$T^2$ dependence observed in heavily overdoped non-superconducting sample.

A pseudogap-like crossover temperature $T^*$ is identified, resembling cuprate phase diagrams.

Abstract

We report electronic transport measurements on single crystals of NaFe$_{1-x}$Co$_x$As system. We found that the cotangent of Hall angle, cot$\theta_{\rm H}$, follows $T^4$ for the parent compound with filamentary superconductivity and $T^2$ for the heavily-overdoped non-superconducting sample. While it exhibits approximately $T^3$-dependence in all the superconducting samples, suggesting this behaivor is associated with bulk superconductivity in ferropnictides. A deviation develops below a characteristic temperature $T^*$ well above the structural and superconducting transitions, accompanied by a departure from power-law temperature dependence in resistivity. The doping dependence of $T^*$ resembles the crossover line of pseudogap phase in cuprates.