Power-law Temperature Dependent Hall Angle in the Normal State and its Correlation with Superconductivity in iron-pnictides

TL;DR

This study reveals a power-law temperature dependence of the Hall angle in iron-pnictides' normal state, with a key change in the exponent near the onset of superconductivity, indicating a link between normal state properties and superconductivity.

Contribution

It identifies a doping-dependent power-law behavior of the Hall angle in iron-pnictides and links the change in exponent to the emergence of superconductivity, providing new insights into high-temperature superconductivity mechanisms.

Findings

Power-law Hall angle dependence with temperature, cotθ_H ∝ T^β.

β ≈ 4 in parent and underdoped samples; β ≈ 3 in superconducting samples.

β changes from 4 to 3 near the doping level where superconductivity appears.

Abstract

We report Hall measurement of the normal state in K- and Co-doped BaFe$_2$As$_2$, as well NaFe$_{1-x}$Co$_x$As. We found that a power-law temperature dependence of Hall angle, cot$\theta_{\rm H}$$\propto$ $T^\beta$, prevails in normal state with temperature range well above the structural, spin-density-wave and superconducting transitions for the all samples with various doping levels. The power $\beta$ is nearly 4 for the parent compounds and the heavily underdoped samples, while around 3 for the superconducting samples. The $\beta$ suddenly changes from 4 to 3 at a doping level that is close to the emergence of superconductivity. It suggests that the $\beta$ of $\sim 3$ is clearly tied to the superconductivity. Our data suggest that, similar to cuprates, there exists a connection between the physics in the normal state and superconductivity of iron-pnictides. These findings shed light on the mechanism of high-temperature superconductivity.