Emerging symmetric strain response and weakening nematic fluctuations in strongly hole-doped iron-based superconductors

TL;DR

This study reveals a dominant symmetric strain response and diminished nematic fluctuations in strongly hole-doped iron-based superconductors, challenging previous notions of nematic order and its role in superconductivity.

Contribution

It demonstrates the emergence of a giant symmetric strain response and the weakening of nematic fluctuations without a change in symmetry channel, revising current understanding of nematicity in these materials.

Findings

Giant in-plane symmetric strain response observed

Weakened nematic fluctuations at high hole doping

No evidence of nematic-ordered state in AFe₂As₂ superconductors

Abstract

Electronic nematicity is often found in unconventional superconductors, suggesting its relevance for electronic pairing. In the strongly hole-doped iron-based superconductors, the symmetry channel and strength of the nematic fluctuations, as well as the possible presence of long-range nematic order, remain controversial. Here, we address these questions using transport measurements under elastic strain. By decomposing the strain response into the appropriate symmetry channels, we demonstrate the emergence of a giant in-plane symmetric contribution, associated with the growth of both strong electronic correlations and the sensitivity of these correlations to strain. We find weakened remnants of the nematic fluctuations that are present at optimal doping, but no change in the symmetry channel of nematic fluctuations with hole doping. Furthermore, we find no evidence for a nematic-ordered state in the AFe$_2$As$_2$(A = K, Rb, Cs) superconductors. These results revise the current understanding of nematicity in hole-doped iron-based superconductors.