Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sharp magnetization jump at the first-order superconducting transition
  in Sr2RuO4   The magnetization and magnetic torque of a high-quality single crystal of
Sr$_2$RuO$_4$ have been measured down to 0.1 K under a precise control of the
magnetic-field orientation. When the magnetic field is applied exactly parallel
to the $ab$ plane, a sharp magnetization jump $4\pi\delta M$ of $(0.74 \pm
0.15)$ G at the upper critical field $H_{{\rm c2},{ab}} \sim 15$ kOe with a
field hysteresis of 100 Oe is observed at low temperatures, evidencing a
first-order superconducting-normal transition. A strong magnetic torque
appearing when $H$ is slightly tilted away from the $ab$ plane confirms an
intrinsic anisotropy $\varGamma=\xi_a/\xi_c$ of as large as 60 even at 100 mK,
in contrast with the observed $H_{{\rm c2}}$ anisotropy of $\sim 20$. The
present results raise fundamental issues in both the existing spin-triplet and
spin-singlet scenarios, providing, in turn, crucial hints toward the resolution
of the superconducting nature of Sr$_2$RuO$_4$.

18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph