Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Direct Observation of Valley-polarized Topological Edge States in
  Designer Surface Plasmon Crystals   The extensive research of two-dimensional layered materials has revealed that
valleys, as energy extrema in momentum space, could offer a new degree of
freedom for carrying information. Based on this concept, researchers have
predicted valley-Hall topological insulators which could support
valley-polarized edge states at non-trivial domain walls. Recently, several
kinds of photonic or sonic crystals have been proposed as classical
counterparts of valley-Hall topological insulators. However, direct
experimental observation of valley-polarized edge states in photonic crystals
is still difficult until now. Here, we demonstrate a designer surface plasmon
crystal comprising metallic patterns deposited on a dielectric substrate, which
can become a valley-Hall photonic topological insulator by exploiting the
mirror-symmetry-breaking mechanism. Topological edge states with
valley-dependent transport are directly visualized in the microwave regime. The
observed edge states are confirmed to be fully valley-polarized through spatial
Fourier transforms. Topological protection of the edge states at sharp corners
is also experimentally demonstrated.

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The categories of this paper are: quant-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
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The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: stat
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The categories of this paper are: funct-an
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph