Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universal Behavior of Magnetoresistance in Organic Dirac Electron
  Systems   In-plane magnetoresistance for organic massless Dirac electron system (OMDES)
$\alpha$-(BEDT-TTF)$_2$I$_3$ and $\theta$-(BEDT-TTF)$_2$I$_3$ in addition to
possible candidates of the OMDES $\alpha$-(BETS)$_2$I$_3$ and
$\alpha$-(BEDT-STF)$_2$I$_3$, was investigated under hydrostatic pressure. We
have found the universal behavior of the in-plane magnetoresistance under a low
magnetic field perpendicular to two-dimensional plane. As for
$\alpha$-(BEDT-TTF)$_2$I$_3$, the universality was examined with the parameters
of temperature, magnetic field and its direction. We suggest that the universal
magnetoresistance behavior is found even for the gapped state of
$\alpha$-(BEDT-TTF)$_2$I$_3$ under intermediate pressure, when the thermal
energy exceeds the gap.

13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th