Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cyclotron Resonance in the Hidden-Order Phase of URu2Si2   We report the first observation of cyclotron resonance in the hidden-order
phase of ultra-clean URu$_2$Si$_2$ crystals, which allows the full
determination of angle-dependent electron-mass structure of the main
Fermi-surface sheets. We find an anomalous splitting of the sharpest resonance
line under in-plane magnetic-field rotation. This is most naturally explained
by the domain formation, which breaks the fourfold rotational symmetry of the
underlying tetragonal lattice. The results reveal the emergence of an in-plane
mass anisotropy with hot spots along the [110] direction, which can account for
the anisotropic in-plane magnetic susceptibility reported recently. This is
consistent with the `nematic' Fermi liquid state, in which itinerant electrons
have unidirectional correlations.

3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
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The categories of this paper are: astro-ph
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int