Absence of nematic instability in LiFeAs

The relationship among unconventional superconductivity, antiferromagnetism, and nematic order in iron-based superconductors (FeSCs) is still highly debated. In many FeSCs superconductivity is in proximity of a nematically and magnetically ordered state. LiFeAs is an exceptional stoichiometric FeSC becoming superconducting below 18 K without undergoing a structural or magnetic transition. However, some recent experimental studies suggested the existence of finite nematic fluctuations and even a nematic superconducting state. In this paper, we employ elastoresistance as a measure of nematic fluctuations in pristine LiFeAs and compare the findings with the elastoresistance of LiFeAs at low Co and V doping levels as well with that of magnetically and nematically ordering NaFeAs. We find LiFeAs and cobalt-doped LiFeAs far away from a nematic instability.