Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Breakdown of spin-to-helicity locking at the nanoscale in topological
  photonic crystal edge states   We measure the local near-field spin in topological edge state waveguides
that emulate the quantum spin Hall effect. We reveal a highly structured spin
density distribution that is not linked to a unique pseudospin value. From
experimental near-field real-space maps and numerical calculations, we confirm
that this local structure is essential in understanding the properties of
optical edge states and light-matter interactions. The global spin is reduced
by a factor of 30 in the near field and, for certain frequencies, flipped
compared to the pseudospin measured in the far-field. We experimentally reveal
the influence of higher-order Bloch harmonics in spin inhomogeneity, leading to
a breakdown in the coupling between local helicity and global spin.

10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
28
The categories of this paper are: alg-geom