Topological states, originated from interactions between internal degree of
freedoms (like spin and orbital) in each site and crystalline symmetries, offer
a new paradigm to manipulate electrons and classical waves. The accessibility
of spin degree of freedom has motivated much attention on spin-related
topological physics. However, intriguing topological physics related to
atomic-orbital parity, another binary degree of freedom, have not been
exploited since accessing approaches on atomic orbitals are not well developed.
Here, we theoretically discover spectral splitting of
atomic-orbital-parity-dependent second-order topological states on a
designer-plasmonic Kagome metasurface, and experimentally demonstrate it by
exploiting the easy controllability of metaatoms. Unlike previous
demonstrations on Hermitian higher-order topological insulators, radiative
non-Hermicity of the metasurface enables far-field access into
metaatomic-orbital-parity-dependent topological states with polarized
illuminations. The atomic-orbital parity degree of freedom may generate more
intriguing topological physics by interacting with different crystalline
symmetries, and promise applications in polarization-multiplexing topological
lasing and quantum emitters.Comment: 19 pages, 4 figure