Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multiferroic Two-Dimensional Materials   The relation between unusual Mexican-hat band dispersion, ferromagnetism and
ferroelasticity is investigated using a combination of analytical,
first-principles and phenomenological methods. The class of material with
Mexican-hat band edge is studied using the $\alpha$-SnO monolayer as a
prototype. Such band edge causes a van Hove singularity diverging with
$\frac{1}{\sqrt{E}}$, and in p-type material leads to spatial and/or
time-reversal spontaneous symmetry breaking. We show that an unexpected
multiferroic phase is obtained in a range of hole density for which the
material presents ferromagnetism and ferroelasticity simultaneously.

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The categories of this paper are: math-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-th
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The categories of this paper are: math
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The categories of this paper are: physics
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The categories of this paper are: funct-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ