Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spontaneous vs. piezoelectric polarization in III-V nitrides: conceptual
  aspects and practical consequences   Macroscopic polarization plays a major role in determining the optical and
electrical properties of nitride nanostructures via polarization-induced
built-in electrostatic fields. While currently fashionable, this field of
endeavour is still by far in its early infancy. Here we contribute some
clarifications on the conceptual issues involved in determining built-in fields
in III-V nitride nanostructures, sorting out in particular the roles of
spontaneous and piezoelectric polarization.

7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
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The categories of this paper are: econ
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th