Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Design and operation of a microfabricated phonon spectrometer utilizing
  superconducting tunnel junctions as phonon transducers   In order to fully understand nanoscale heat transport it is necessary to
spectrally characterize phonon transmission in nanostructures. Towards this
goal we have developed a microfabricated phonon spectrometer. We utilize
microfabricated superconducting tunnel junction-based (STJ) phonon transducers
for the emission and detection of tunable, non-thermal, and spectrally resolved
acoustic phonons, with frequencies ranging from ~100 to ~870 GHz, in silicon
microstructures. We show that phonon spectroscopy with STJs offers a spectral
resolution of ~15-20 GHz, which is ~20 times better than thermal conductance
measurements, for probing nanoscale phonon transport. The STJs are Al-AlxOy-Al
tunnel junctions and phonon emission and detection occurs via quasiparticle
excitation and decay transitions that occur in the superconducting films. We
elaborate on the design geometry and constraints of the spectrometer, the
fabrication techniques, and the low-noise instrumentation that are essential
for successful application of this technique for nanoscale phonon studies. We
discuss the spectral distribution of phonons emitted by an STJ emitter and the
efficiency of their detection by an STJ detector. We demonstrate that the
phonons propagate ballistically through a silicon microstructure, and that
submicron spatial resolution is realizable in a design such as ours. Spectrally
resolved measurements of phonon transport in nanoscale structures and
nanomaterials will further the engineering and exploitation of phonons, and
thus have important ramifications for nanoscale thermal transport as well as
the burgeoning field of nanophononics.

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The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int