  Nematicity plays an important role in the physics of iron-based
superconductors (IBS). Its microscopic origin and in particular its importance
for the mechanism of high-temperature superconductivity itself are highly
debated. A crucial knowledge in this regard is the degree to which the nematic
order influences the electronic structure of these materials. Earlier
angle-resolved photoemission spectroscopy (ARPES) studies found that the effect
is dramatic in three families of IBS including 11, 111 and 122 compounds:
energy splitting reaches 70 meV and Fermi surface becomes noticeably distorted.
More recent experiments, however, reported significantly lower energy scale in
11 and 111 families, thus questioning the degree and universality of the impact
of nematicity on the electronic structure of IBS. Here we revisit the
electronic structure of undoped parent BaFe2As2 (122 family). Our systematic
ARPES study including the detailed temperature and photon energy dependencies
points to the significantly smaller energy scale also in this family of
materials, thus establishing the universal scale of this phenomenon in IBS. Our
results form a necessary quantitative basis for theories of high-temperature
superconductivity focused on the nematicity.
