Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultrafast light-induced shear strain probed by time-resolved X-ray
  diffraction: the model multiferroic BiFeO$_3$ as a case study   Enabling the light-control of complex systems on ultra-short timescales gives
rise to rich physics with promising applications. While crucial, the
quantitative determination of both the longitudinal and shear photo-induced
strains still remains challenging. Here, by scrutinizing asymmetric Bragg peaks
pairs $(\pm h01)$ using picosecond time-resolved X-ray diffraction experiments
in BiFeO$_3$, we simultaneously determine the longitudinal and shear strains.
The relative amplitude of those strains can be explained only if both thermal
and non-thermal processes contribute to the acoustic phonon photogeneration
process. Importantly, we also reveal a difference of the dynamical response of
the longitudinal strain with respect to the shear one due to an interplay of
quasi-longitudinal and quasi-transverse acoustic modes, well reproduced by our
model.

3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: eess
32
The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph