Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anisotropic surface transport in topological insulators in proximity to
  a helical spin density wave   We study the effects of spatially localized breakdown of time reversal
symmetry on the surface of a topological insulator (TI) due to proximity to a
helical spin density wave (HSDW). The HSDW acts like an externally applied
one-dimensional periodic(magnetic) potential for the spins on the surface of
the TI, rendering the Dirac cone on the TI surface highly anisotropic. The
decrease of group velocity along the direction $\hat{x}$ of the applied spin
potential is twice as much as that perpendicular to $\hat{x}$. At the Brillouin
zone boundaries (BZB) it also gives rise to new semi-Dirac points which have
linear dispersion along $\hat{x}$ but quadratic dispersion perpendicular to
$\hat{x}$. The group velocity of electrons at these new semi-Dirac points is
also shown to be highly anisotropic. Experiments using TI systems on
multiferroic substrates should realize our predictions. We further discuss the
effects of other forms of spin density wave on the surface transport property
of topological insulator.

27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph