  Silicene, the two-dimensional allotrope of silicon, is predicted to exist in
a low-buckled honeycomb lattice, characterized by semimetallic electronic bands
with graphenelike energy-momentum dispersions around the Fermi level
(represented by touching Dirac cones). Single layers of silicene are mostly
synthesized by depositing silicon on top of silver, where, however, the
different phases observed to date are so strongly hybridized with the substrate
that not only the Dirac cones, but also the whole valence and conduction states
of ideal silicene appear to be lost. Here, we provide evidence that at least
part of this semimetallic behavior is preserved by the coexistence of more
silicene phases, epitaxially grown on Ag(111). In particular, we combine
electron energy loss spectroscopy and time-dependent density functional theory
to characterize the low-energy plasmon of a multiphase-silicene/Ag(111) sample,
prepared at controlled silicon coverage and growth temperature. We find that
this mode survives the interaction with the substrate, being perfectly matched
with the {\pi}-like plasmon of ideal silicene. We therefore suggest that the
weakened interaction of multiphase silicene with the substrate may provide a
unique platform with the potential to develop different applications based on
two-dimensional silicon systems.
