  Achieving robust transport has attracted much attention in both electronic
and photonic systems. Time-reversal invariant photonic crystal can be employed
to realize backscattering-immune chiral state, but the chiral bandgap is
topologically trivial. Here, we designed and fabricated a metacrystal
comprising non-resonant meta-atoms sandwiched between two metallic plates and
the system exhibits topological phase transition as established by group
classification. The nontrivial bandgap was confirmed by experimentally measured
transmission spectra, calculated nonzero spin Chern number and Z2 index.
Gapless spin-filtered edge states were demonstrated experimentally by measuring
the magnitude and phase of the fields. The transpsort robustness of the edge
states were also observed when an obstacle is introduced near the edge.
