  Double-layered Sr3Ru2O7 has received phenomenal consideration because it
exhibits a plethora of exotic phases when perturbed. New phases emerge with the
application of pressure, magnetic field, or doping. Here we show that creating
a surface is an alternative and effective way to reveal hidden phases that are
different from those seen in the bulk by investigating the surface properties
of Sr3(Ru1-xMnx)2O7. Driven by the tilt distortion of RuO6 octahedra, the
surface of Sr3Ru2O7 is less metallic than the bulk. In contrast, because of the
vanishing of tilt and enhanced rotation with Mn-doping, the surface of
Sr3(Ru0.84Mn0.16)2O7 is metallic while the bulk is insulating. Our result
demonstrates that the electronic and structural properties at the surface are
intimately coupled and consistent with quasi two-dimensional character.
