Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Three-dimensional topological photonic crystal with a single surface
  Dirac cone   A single Dirac cone on the surface is the hallmark of three-dimensional (3D)
topological insulators, where the double degeneracy at the Dirac point is
protected by time-reversal symmetry and the spin-splitting away from the point
is provided by the spin-orbital coupling. Here we predict a single Dirac-cone
surface state in a 3D photonic crystal, where the degeneracy at the Dirac point
is protected by a nonsymmorphic glide reflection and the linear splitting away
from it is enabled by breaking time-reversal symmetry. Such a gapless surface
state is fully robust against random disorder of any type. This bosonic
topological band structure is achieved by applying alternating magnetization to
gap out the 3D "generalized Dirac points" discovered in the bulk of our
crystal. The $Z_2$ bulk invariant is characterized through the evolution of
Wannier centers. Our proposal--readily realizable using ferrimagnetic materials
at microwave frequencies--can also be regarded as the photonic analog of
topological crystalline insulators, providing the first 3D bosonic
symmetry-protected topological system.

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The categories of this paper are: supr-con
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The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ex
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The categories of this paper are: q-alg
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The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas