  In correlated electrons system, quantum melting of electronic crystalline
phase often gives rise to many novel electronic phases. In cuprates
superconductors, melting the Mott insulating phase with carrier doping leads to
a quantum version of liquid crystal phase, the electronic nematicity, which
breaks the rotational symmetry and exhibits a tight twist with high-temperature
superconductivity. Recently, the electronic nematicity has also been observed
in Fe-based superconductors. However, whether it shares a similar scenario with
its cuprates counterpart is still elusive. Here, by measuring nuclear magnetic
resonance in CsFe2As2, a prototypical Fe-based superconductor perceived to have
evolved from a Mott insulating phase at 3d5 configuration, we report
anisotropic quadruple broadening effect as a direct result of local rotational
symmetry breaking. For the first time, clear connection between the Mott
insulating phase and the electronic nematicity can be established and
generalized to the Fe-based superconductors. This finding would promote a
universal understanding on electronic nematicity and its relation with
high-temperature superconductivity.

Superconductivity;Materials Science;Strongly Correlated Electrons