Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Emergent Momentum-Space Skyrmion Texture on the Surface of Topological
  Insulators   The quantum anomalous Hall effect has been theoretically predicted and
experimentally verified in magnetic topological insulators. In addition, the
surface states of these materials exhibit a hedgehog-like "spin" texture in
momentum space. Here, we apply the previously formulated low-energy model for
Bi$_2$Se$_3$, a parent compound for magnetic topological insulators, to a slab
geometry in which an exchange field acts only within one of the surface layers.
In this sample set up, the hedgehog transforms into a skyrmion texture beyond a
critical exchange field. This critical field marks a transition between two
topologically distinct phases. The topological phase transition takes place
without energy gap closing at the Fermi level and leaves the transverse Hall
conductance unchanged and quantized to $e^2/2h$. The momentum-space skyrmion
texture persists in a finite field range. It may find its realization in hybrid
heterostructures with an interface between a three-dimensional topological
insulator and a ferromagnetic insulator.

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The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph