Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Optical Activity of the Dark Exciton   We present a phenomenological model to consider the effect of shape symmetry
breaking on the optical properties of self-assembled quantum dots. We compare
between quantum dots with two-fold rotational and two reflections ($C_{2v}$)
symmetry and quantum dots in which this symmetry is reduced by perturbation to
one reflection only ($C_{s}$). We show that this symmetry reduction drastically
affects the optical activity of the dark exciton.
  In symmetric quantum dots, one of the dark exciton eigenstate is totally dark
and the other, due to heavy- and light-hole mixing, has a small dipole moment
polarized along the symmetry axis (growth direction) of the quantum dot. In
non-symmetric quantum dots, the two dark excitons' eigenstates are mixed with
the bright excitons' eigenstates which have cross-linearly polarized
perpendicular to the growth direction dipole moments. As a result of this
mixing one of the dark exciton eigenstate is dark while the other one does have
dipole moment which is linearly polarized normal to the growth direction, like
the lower energy bright exciton eigenstate.
  Our model agrees well with recently obtained experimental data.

28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
8
The categories of this paper are: hep-ex