Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetism and Superconductivity in Ferromagnetic Heavy Fermion System
  UCoGe under In-plane Magnetic Fields   We study the ferromagnetic superconductor UCoGe at ambient pressure under
$ab$-plane magnetic fields $\vec{H}$ which are perpendicular to the
ferromagnetic easy axis. It is shown that, by taking into account the
Dyaloshinskii-Moriya interaction arising from the zigzag chain crystal
structure of UCoGe, we can qualitatively explain the experimentally observed
in-plane anisotropy for critical magnetic fields of the paramagnetic
transition. Because of this strong dependence on the magnetic field direction,
upper critical fields of superconductivity, which is mediated by ferromagnetic
spin fluctuations, also become strongly anisotropic. The experimental
observation of "S-shaped" $H_{c2}\parallel b$-axis is qualitatively explained
as a result of enhancement of the spin fluctuations due to decreased Curie
temperature by the $b$-axis magnetic field. We also show that the S-shaped
$H_{c2}$ is accompanied by a rotation of the $d$-vector, which would be a key
to understand the experiments not only at ambient pressure but also under
pressure.

24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom