Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantized electromagnetic response of three-dimensional chiral
  topological insulators   Protected by the chiral symmetry, three dimensional chiral topological
insulators are characterized by an integer-valued topological invariant. How
this invariant could emerge in physical observables is an important question.
Here we show that the magneto-electric polarization can identify the
integer-valued invariant if we gap the system without coating a quantum Hall
layer on the surface. The quantized response is demonstrated to be robust
against weak perturbations. We also study the topological properties by
adiabatically coupling two nontrivial phases, and find that gapless states
appear and are localized at the boundary region. Finally, an experimental
scheme is proposed to realize the Hamiltonian and measure the quantized
response with ultracold atoms in optical lattices.

3
The categories of this paper are: physics
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg