Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theory of parametric amplification in in superlattices   We consider a high-frequency response of electrons in a single miniband of
superlattice subject to dc and ac electric fields. We show that Bragg
reflections in miniband result in a parametric resonance which is detectable
using ac probe field. We establish theoretical feasibility of phase-sensitive
THz amplification at the resonance. The parametric amplification does not
require operation in conditions of negative differential conductance. This
prevents a formation of destructive high-field domains inside the superlattice.

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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph