Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Vortex lattice transition in D-wave superconductors   Making use of the extended Ginzburg Landau theory, which includes the fourth
order derivative term, we study the vortex state in a magnetic field parallel
to the $ c$ axis. The vortex core structure is distorted due to this higher
order term, which reveals t he fourfold symmetry. Futher, this distortion gives
rise to the core interaction energy, which favo rs a square lattice tilted by
$45^\circ$ from the $a$ axis. The critical field of this transition is
determined. The magnetization diverges at the transition. This suggests the
transition is of the fi rst order.

16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci