Simultaneous Vanishing of the Nematic Electronic State and the Structural Orthorhombicity in NaFe$_{1-x}$Co$_x$As Single Crystals

TL;DR

This study reveals that in NaFe$_{1-x}$Co$_x$As, the nematic electronic state and structural orthorhombicity vanish simultaneously with doping, highlighting their close relationship and implications for superconductivity.

Contribution

The paper provides the first direct experimental evidence that nematicity and structural orthorhombicity disappear together in NaFe$_{1-x}$Co$_x$As, clarifying their interplay.

Findings

Nematic electronic state vanishes with structural transition.

Antiferromagnetic state persists at higher doping levels.

Close relationship between nematicity and superconductivity.

Abstract

We have carried out in-plane resistivity measurements under a uniaxial pressure in NaFe$_{1-x}$Co$_x$As single crystals. A clear distinction of the in-plane resistivity $\rho_a$ and $\rho_b$ with the uniaxial pressure along $b$-axis was discovered in the parent and underdoped regime with the doping level up to about x=0.025$\pm$0.002. From the deviating point of $\rho_a$ and $\rho_b$, and the unique kinky structure of resistivity together with the published data we determined the temperatures for the nematic, structural and antiferromagnetic transitions. It is clearly shown that the nematic electronic state vanishes simultaneously with the structural transition. The antiferromagnetic state disappears however at a lower doping level. Our results, in combination with the data in BaFe$_{2-x}$Co$_x$As$_2$, indicate a close relationship between nematicity and superconductivity.