Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fermi surface in the hidden-order state of URu$_2$Si$_2$ under intense
  pulsed magnetic fields up to 81~T   We present measurements of the resistivity $\rho_{x,x}$ of URu2Si2
high-quality single crystals in pulsed high magnetic fields up to 81~T at a
temperature of 1.4~K and up to 60~T at temperatures down to 100~mK. For a field
\textbf{H} applied along the magnetic easy-axis \textbf{c}, a strong
sample-dependence of the low-temperature resistivity in the hidden-order phase
is attributed to a high carrier mobility. The interplay between the magnetic
and orbital properties is emphasized by the angle-dependence of the phase
diagram, where magnetic transition fields and crossover fields related to the
Fermi surface properties follow a 1/$\cos\theta$-law, $\theta$ being the angle
between \textbf{H} and \textbf{c}. For $\mathbf{H}\parallel\mathbf{c}$, a
crossover defined at a kink of $\rho_{x,x}$, as initially reported in [Shishido
et al., Phys. Rev. Lett. \textbf{102}, 156403 (2009)], is found to be strongly
sample-dependent: its characteristic field $\mu_0H^*$ varies from $\simeq20$~T
in our best sample with a residual resistivity ratio RRR of $225$ to
$\simeq25$~T in a sample with a RRR of $90$. A second crossover is defined at
the maximum of $\rho_{x,x}$ at the sample-independent characteristic field
$\mu_0H_{\rho,max}^{LT}\simeq30$~T. Fourier analyzes of SdH oscillations show
that $H_{\rho,max}^{LT}$ coincides with a sudden modification of the Fermi
surface, while $H^*$ lies in a regime where the Fermi surface is smoothly
modified. For $\mathbf{H}\parallel\mathbf{a}$, i) no phase transition is
observed at low temperature and the system remains in the hidden-order phase up
to 81~T, ii) quantum oscillations surviving up to 7~K are related to a new and
almost-spherical orbit - for the first time observed here - at the frequency
$F_\lambda\simeq1400$~T and associated with a low effective mass
$m^*_\lambda=(1\pm0.5)\cdot m_0$, and iii) no Fermi surface modification occurs
up to 81~T.

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The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: math
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: plasm-ph