Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hole-lattice Coupling and Photo-induced Insulator-Metal Transition in
  VO$_2$   Photo-induced insulator-metal transition in VO$_2$ and the related transient
and multi-timescale structural dynamics upon photoexcitation are explained
within a unified framework. Holes created by photoexcitation weaken the V-V
bonds and eventually break V-V dimers in the M$_1$ phase of VO$_2$ when the
laser fluence reaches a critical value. The breaking of the V-V bonds in turn
leads to an immediate electronic phase transition from an insulating to a
metallic state while the crystal lattice remains monoclinic in shape. The
coupling between excited electrons and the 6.0 THz phonon mode is found to be
responsible for the observed zig-zag motion of V atoms upon photoexcitation and
is consistent with coherent phonon experiments.

28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
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The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio