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

Electronic nematicity is often found in unconventional superconductors, suggesting its rele-
vance 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 sym-
metric 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 fluc-
tuations that are present at optimal doping, but no change in the symmetry channel of
nematic fluctuations with hole doping. Furthermore, we find no indication of a nematic-
ordered state in the AFe2As2 (A =K, Rb, Cs) superconductors. These results revise the
current understanding of nematicity in hole-doped iron-based superconductors.