Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Surface polar states and pyroelectricity in ferroelastics induced by
  flexo-roto field   Theoretical analysis based on the Landau-Ginzburg-Devonshire (LGD) theory is
used to show that the joint action of flexoelectric effect and rotostriction
leads to a large spontaneous in-plane polarization (~ 1-5 muC/cm2) and
pyroelectric coefficient (~10^-3 C/m2K) in the vicinity of surfaces of
otherwise non-ferroelectric ferroelastics, such as SrTiO3, with static
octahedral rotations. The origin of the improper polarization and
pyroelectricity is an electric field we name flexo-roto field whose strength is
proportional to the convolution of the flexoelectric and rotostriction tensors
with octahedral tilts and their gradients. Flexo-roto field should exist at
surfaces and interfaces in all structures with static octahedral rotations, and
thus it can induce surface polar states and pyroelectricity in a large class of
otherwise nonpolar materials.

9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex