  Nematic state, where the system is translationally invariant but breaks the
rotational symmetry, has drawn great attentions recently due to experimental
observations of such a state in both cuprates and iron-based superconductors.
The mechanism of nematicity that is likely tied to the pairing mechanism of
high-Tc, however, still remains controversial. Here, we studied the electronic
structure of multilayer FeSe film by angle-resolved photoemission spectroscopy
(ARPES). We found that the FeSe film enters the nematic state around 125 K,
while the electronic signature of long range magnetic order has not been
observed down to 20K indicating the non-magnetic origin of the nematicity. The
band reconstruction in the nematic state is characterized by the splitting of
the dxz and dyz bands. More intriguingly, such energy splitting is strong
momentum dependent with the largest band splitting of ~80meV at the zone
corner. The simple on-site ferro-orbital ordering is insufficient to reproduce
the nontrivial momentum dependence of the band reconstruction. Instead, our
results suggest that the nearest-neighbor hopping of dxz and dyz is highly
anisotropic in the nematic state, the origin of which holds the key in
understanding the nematicity in iron-based superconductors.
