  Topological characteristics of energy bands, such as Dirac/Weyl nodes, have
attracted substantial interest in condensed matter systems as well as in
classical wave systems. Among these energy bands, the type-II Dirac point is a
nodal degeneracy with tilted conical dispersion, leading to a peculiar crossing
dispersion in the constant energy plane. Such nodal points have recently been
found in electronic materials. The analogous topological feature in photonic
systems remains a theoretical curiosity, with experimental realization expected
to be challenging. Here, we experimentally realize the type-II Dirac point
using a planar metasurface architecture, where the band degeneracy point is
protected by the underlying mirror symmetry of the metasurface. Gapless edge
modes are found and measured at the boundary between the different domains of
the symmetry-broken metasurface. Our work shows that metasurfaces are simple
and practical platforms for realizing electromagnetic type-II Dirac points, and
their planar structure is a distinct advantage that facilitates applications in
two-dimensional topological photonics.
