Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Piezoelectric Polar Nano Regions and Relaxation-Coupled Resonances in
  Relaxor Ferroelectrics   \indent It is a generally accepted fact that the unique dielectric properties
of relaxor ferroelectrics are related to the formation of polar nanoregion
(PNRs). Less well recognized is the corollary that, because they are polar and
therefore lack inversion symmetry, PNRs are also piezoelectric at the nanoscale
and can therefore behave as nanoresonators. Using the particular relaxor
ferroelectric K$_{\tt1-x}$Li$_{\tt x}$TaO$_{\tt 3}$ (KLT), we show that, when
electrically excited into oscillation, these piezoelectric nanoresonators can
drive macroscopic electro-mechanical resonances. Unexpectedly however, pairs of
coupled resonances are observed, with one of the two exhibiting a
characteristic Fano-like lineshape. The complex resonance spectra can be
described equally well by two alternative but complementary models both
involving two resonances coupled through a relaxation: a purely classical one
based on two coupled damped harmonic oscillators and a semi-classical based on
two discrete excitations coupled to each other through a continuum. Together,
they provide complementary perspectives on the underlying physics of the
system. Both reproduce the rapid evolution of the resonance spectrum across
three wide temperature ranges, including a phase transition range. In the high
temperature range, the coupling between modes is due to the collective $\pi$
relaxation of the lithium ions within PNRs and in the phase transition range to
"heterophase relaxation" of the surrounding lattice between its high
temperature cubic and low temperature tetragonal phases. The coupling is
suppressed in the intermediate range of the collective $\pi/2$ relaxation of
the lithium ions. Incidentally, the measured dielectric spectra are shown to
bear a surprising but justifiable resemblance to the optical spectra of certain
atomic vapors that exhibit electromagnetically induced transparency.

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The categories of this paper are: hep-ph
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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: bayes-an
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The categories of this paper are: astro-ph
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The categories of this paper are: cs
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The categories of this paper are: physics
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph
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The categories of this paper are: q-fin