Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: High-order Harmonic Generation and its Unconventional Scaling Law in the
  Mott-insulating $\rm{Ca_2RuO_4}$   Competition and cooperation among orders is at the heart of many-body physics
in strongly correlated materials and leads to their rich physical properties.
It is crucial to investigate what impact many-body physics has on extreme
nonlinear optical phenomena, with the possibility of controlling material
properties by light. However, the effect of competing orders and
electron-electron correlations on highly nonlinear optical phenomena has not
yet been experimentally clarified. Here, we investigated high-order harmonic
generation from the Mott-insulating phase of Ca2RuO4. Changing the gap energy
in Ca2RuO4 as a function of temperature, we observed a strong enhancement of
high order harmonic generation at 50 K, increasing up to several hundred times
compared to room temperature. We discovered that this enhancement can be
well-reproduced by an empirical scaling law that depends only on the material
gap energy and photon emission energy. Such scaling law cannot be explained by
a simple two-band model under the single electron approximation. Our results
suggest that the highly nonlinear optical response of strongly correlated
materials is deeply coupled to their electron-electron correlations and
resultant many-body electronic structure.

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The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
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The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: nucl-th
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The categories of this paper are: funct-an