Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metastable ferroelectricity in optically strained $SrTiO_3$   Fluctuating orders in solids are generally considered high-temperature
precursors of broken symmetry phases. However, in some cases these fluctuations
persist to zero temperature and prevent the emergence of long-range order, as
for example observed in quantum spin and dipolar liquids. $SrTiO_3$ is a
quantum paraelectric in which dipolar fluctuations grow when the material is
cooled, although a long-range ferroelectric order never sets in. We show that
the nonlinear excitation of lattice vibrations with mid-infrared optical pulses
can induce polar order in $SrTiO_3$ up to temperatures in excess of 290 K. This
metastable phase, which persists for hours after the optical pump is
interrupted, is evidenced by the appearance of a large second-order optical
nonlinearity that is absent in equilibrium. Hardening of a low-frequency mode
indicates that the polar order may be associated with a photo-induced
ferroelectric phase transition. The spatial distribution of the optically
induced polar domains suggests that a new type of photo-flexoelectric coupling
triggers this effect.

35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin