Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Plasmons in single- and double-component helical liquids: Application to
  two-dimensional topological insulators   The plasmon excitations in proposed single- and double-component helical
liquid (HL) models are investigated within the random-phase approximation, by
calculating the density-density, spin-density and spin-spin waves. The effect
due to broken time-reversal symmetry on intraband-plasmon dispersion relation
in the single-component HL system is analyzed and compared to those of
well-known cases, such as conventional quasi-one-dimensional electron gases and
armchair graphene nanoribbons. The equivalence between the density-density wave
in the single-component HL to the coupled spin-density and density-density
waves in the double-component HL is shown here and explained, in addition to
the difference between intraband and interband-plasmon excitations in these two
systems. Since the two-component HL can physically be thought of as a Kramers
pair in two-dimensional topological insulators, our proposed single-component
HL model with broken time-reversal symmetry, which is an artificial construct,
can be viewed as an "effective" model in this sense and its prediction may be
verified in realistic systems in future experiments.

1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th