Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Conductivity of twin walls - surface junctions in ferroelastics:
  interplay of deformation potential, octahedral rotations, improper
  ferroelectricity and flexoelectric coupling   Electronic and structural phenomena at the twin domain wall-surface junctions
in the ferroelastic materials are analyzed. Carriers accumulation caused by the
strain-induced band structure changes originated via the deformation potential
mechanism, structural order parameter gradient, rotostriction and flexoelectric
coupling is explored. Approximate analytical results show that inhomogeneous
elastic strains, which exist in the vicinity of the twin walls - surface
junctions due to the rotostriction coupling, decrease the local band gap via
the deformation potential and flexoelectric coupling mechanisms. This is the
direct mechanism of the twin walls static conductivity in ferroelastics and, by
extension, in multiferroics and ferroelectrics. On the other hand,
flexoelectric and rotostriction coupling leads to the appearance of the
improper polarization and electric fields proportional to the structural order
parameter gradient in the vicinity of the twin walls - surface junctions. The
"flexo-roto" fields leading to the carrier accumulation are considered as
indirect mechanism of the twin walls conductivity. Comparison of the direct and
indirect mechanisms illustrates complex range of phenomena directly responsible
for domain walls static conductivity in materials with multiple order
parameters.

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The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics