Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlocal Spin Transport as a Probe of Viscous Magnon Fluids   Magnons in ferromagnets behave as a viscous fluid over a length scale, the
momentum-relaxation length, below which momentum-conserving scattering
processes dominate. We show theoretically that in this hydrodynamic regime
viscous effects lead to a sign change in the magnon chemical potential, which
can be detected as a sign change in the nonlocal resistance measured in spin
transport experiments. This sign change is observable when the
injector-detector distance becomes comparable to the momentum-relaxation
length. Taking into account momentum- and spin-relaxation processes, we
consider the quasiconservation laws for momentum and spin in a magnon fluid.
The resulting equations are solved for nonlocal spin transport devices in which
spin is injected and detected via metallic leads. Because of the finite
viscosity we also find a backflow of magnons close to the injector lead. Our
work shows that nonlocal magnon spin transport devices are an attractive
platform to develop and study magnon-fluid dynamics.

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The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
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The categories of this paper are: econ
9
The categories of this paper are: nlin
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The categories of this paper are: supr-con
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The categories of this paper are: hep-th
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph