# Evolution of the nematic susceptibility in LaFe$_{1-x}$Co$_x$AsO

## TL;DR

This study investigates how nematic susceptibility evolves with cobalt doping in LaFeAsO, revealing a suppression and sign change near optimal doping, suggesting a nematic quantum critical point beneath the superconducting phase.

## Contribution

It provides a systematic elastoresistivity analysis of LaFe$_{1-x}$Co$_x$AsO, highlighting the doping-dependent evolution of nematic susceptibility and its complex features.

## Key findings

- Nematic susceptibility is Curie-Weiss-like in all samples.
- Nematic temperature decreases with cobalt doping and changes sign near optimal doping.
- A double-peak feature in nematic susceptibility amplitude suggests multiple contributing effects.

## Abstract

The identification of electronic nematicity across series of iron-based superconductors raises the question of its relationship with superconductivity and other ordered states. Here, we report a systematic elastoresistivity study on LaFe$_{1-x}$Co$_x$AsO single crystals, which have well separated structural and magnetic transition lines. All crystals show Curie-Weiss-like nematic susceptibility in the tetragonal phase. The extracted nematic temperature is monotonically suppressed upon cobalt doping, and changes sign around the optimal doping level, indicating a possible nematic quantum critical point beneath the superconducting dome. The amplitude of nematic susceptibility shows a peculiar double-peak feature. This could be explained by a combined effect of different contributions to the nematic susceptibility, which are amplified at separated doping levels of LaFe$_{1-x}$Co$_x$AsO.