Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical Birefringence and Dichroism of Cuprate Superconductors in the
  THz regime   The presence of optical polarization anisotropies, such as Faraday/Kerr
effects, linear birefringence, and magnetoelectric birefringence are evidence
for broken symmetry states of matter. The recent discovery of a Kerr effect
using near-IR light in the pseudogap phase of the cuprates can be regarded as a
strong evidence for a spontaneous symmetry breaking and the existence of an
anomalous long-range ordered state. In this work we present a high precision
study of the polarimetry properties of the cuprates in the THz regime. While no
Faraday effect was found in this frequency range to the limits of our
experimental uncertainty (1.3 milli-radian or 0.07$^\circ$), a small but
significant polarization rotation was detected that derives from an anomalous
linear dichroism. In YBa$_2$Cu$_3$O$_y$ the effect has a temperature onset that
mirrors the pseudogap temperature T$^*$ and is enhanced in magnitude in
underdoped samples. In $x=1/8$ La$_{2-x}$Ba$_{x}$CuO$_4$, the effect onsets
above room temperature, but shows a dramatic enhancement near a temperature
scale known to be associated with spin and charge ordered states. These
features are consistent with a loss of both C$_4$ rotation and mirror symmetry
in the electronic structure of the CuO$_2$ planes in the pseudogap state.

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The categories of this paper are: stat
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: physics
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: adap-org
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The categories of this paper are: gr-qc