Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phonon splitting and anomalous enhancement of infrared-active modes in
  BaFe$_2$As$_2$   We present a comprehensive infrared spectroscopic study of lattice dynamics
in the pnictide parent compound BaFe$_2$As$_2$. In the tetragonal structural
phase, we observe the two degenerate symmetry-allowed in-plane infrared active
phonon modes. Following the structural transition from the tetragonal to
orthorhombic phase, we observe splitting into four non-degenerate phonon modes
and a significant phonon strength enhancement. These detailed data allow us to
provide a physical explanation for the anomalous phonon strength enhancement as
the result of anisotropic conductivity due to Hund's coupling.

25
The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph