Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical conductivity of colossal magnetorestistance compounds: Role of
  orbital degeneracy in the ferromagnetic phase   Recent optical conductivity $\sigma(\omega)$ experiments have revealed an
anomalous spectral distribution in the ferromagnetic phase of the perovskite
system $La_{1-x}Sr_xMnO_3$. Using finite temperature diagonalization techniques
we investigate $\sigma(\omega)$ for a model that contains only the
$e_g$-orbital degrees of freedom. Due to strong correlations the orbital model
appears as a generalized t-J model with anisotopic interactions and 3-site
hopping. In the orbital t-J model $\sigma(\omega)$ is characterized by a broad
incoherent spectrum with increasing intensity as temperature is lowered, and a
Drude peak with small weight, consistent with experiment. Our calculations for
two-dimensional systems, which may have some particular relevance for the
double-layer manganites, show that the scattering from orbital fluctuations can
explain the order of magnitude of the incoherent part of $\sigma(\omega)$ in
the low temperature ferromagnetic phase. Moreover orbital correlation functions
are studied and it is shown that $x^2$-$y^2$ orbital order is prefered in the
doped planar model at low temperature.

8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
16
The categories of this paper are: stat
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg