Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Shubnikov de Haas effect in the metallic state of Na$_{0.3}$CoO$_2$   Shubnikov de Haas oscillations for two well defined frequencies,
corresponding respectively to areas of 0.8 and 1.36% of the first Brillouin
zone (FBZ), were observed in single crystals of Na$_{0.3}$CoO$_2$. The
existence of Na superstructures in Na$_{0.3}$CoO$_2$, coupled with this
observation, suggests the possibility that the periods are due to the
reconstruction of the large Fermi surface around the $\Gamma$ point. An
alternative interpretation in terms of the long sought-after
$\epsilon_g^\prime$ pockets is also considered but found to be incompatible
with existing specific heat data.

36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int