Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Graphene: new bridge between condensed matter physics and quantum
  electrodynamics   Graphene is the first example of truly two-dimensional crystals - it's just
one layer of carbon atoms. It turns out to be a gapless semiconductor with
unique electronic properties resulting from the fact that charge carriers in
graphene demonstrate charge-conjugation symmetry between electrons and holes
and possess an internal degree of freedom similar to ``chirality'' for
ultrarelativistic elementary particles. It provides unexpected bridge between
condensed matter physics and quantum electrodynamics (QED). In particular, the
relativistic Zitterbewegung leads to the minimum conductivity of order of
conductance quantum $e^2/h$ in the limit of zero doping; the concept of Klein
paradox (tunneling of relativistic particles) provides an essential insight
into electron propagation through potential barriers; vacuum polarization
around charge impurities is essential for understanding of high electron
mobility in graphene; index theorem explains anomalous quantum Hall effect.

36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph