Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Making Massless Dirac Fermions from Patterned Two-Dimensional Electron
  Gases   Analysis of the electronic structure of an ordinary two-dimensional electron
gas (2DEG) under an appropriate external periodic potential of hexagonal
symmetry reveals that massless Dirac fermions are generated near the corners of
the supercell Brillouin zone. The required potential parameters are found to be
achievable under or close to laboratory conditions. Moreover, the group
velocity is tunable by changing either the effective mass of the 2DEG or the
lattice parameter of the external potential, and it is insensitive to the
potential amplitude. The finding should provide a new class of systems other
than graphene for investigating and exploiting massless Dirac fermions using
2DEGs in semiconductors.

2
The categories of this paper are: math
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex