Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Soft tilt and rotational modes in the hybrid improper ferroelectric
  Ca$_{3}$Mn$_{2}$O$_{7}$   Raman spectroscopy is employed to probe directly the soft rotation and
tilting modes, which are two primary order parameters predicted in the hybrid
improper ferroelectric material Ca$_3$Mn$_2$O$_7$. We observe a giant softening
of the 107-cm$^{-1}$ octahedron tilting mode by 26~cm$^{-1}$, on heating
through the structural transition from a ferroelectric to paraelectric
orthorhombic phase. This is contrasted by a small softening of the
150-cm$^{-1}$ rotational mode by 6~cm$^{-1}$. In the intermediate phase, the
competing soft modes with different symmetries coexist, bringing about
many-faceted anomalies in spin excitations and lattice vibrations. Our work
demonstrates that the soft rotation and tilt patterns, relying on a
phase-transition path, are a key factor in determining ferroelectric, magnetic,
and lattice properties of Ca$_3$Mn$_2$O$_7$.

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The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
2
The categories of this paper are: math