Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Coherent phonon dynamics at the martensitic phase transition of Ni_2MnGa   We use time-resolved optical reflectivity to study the laser stimulated
dynamics in the magnetic shape memory alloy Ni_2MnGa. We observe two coherent
optical phonons, at 1.2 THz in the martensite phase and at 0.7 THz in the
pre-martensite phase, which we interpret as a zone-folded acoustic phonon and a
heavily damped amplitudon respectively. In the martensite phase the martensitic
phase transition can be induced by a fs laser pulse on a timescale of a few ps.

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The categories of this paper are: math
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
6
The categories of this paper are: astro-ph
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The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
16
The categories of this paper are: stat