Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Activated hopping transport in nematic conducting aerogel at low
  temperatures   The transport properties of nematic aerogels, which consist of highly
oriented Al$_2$O$_3\cdot$SiO$_2$ nanofibers coated with a graphene shell with a
large number of defects, are studied. The temperature dependences of the
electrical resistivity in the range of 9-40K strictly follow the formula
derived to describe the variable range hopping (VRH) conductivity, in which
exponent $\alpha$ changes from 0.4 to 0.9 when the number of layers in the
graphene shell decreases from 4-6 to 1-2. The dependence of $\alpha$ on the
shell thickness can be explained by a simultaneous change in the dimensionality
of hopping transport and the character of the energy dependence of the density
of localized states near the Fermi level. The fact that $\alpha$ approaches
unity at the minimum graphene shell thickness indicates a gradual transition
from VRH transport to nearest neighbor hopping (NNH) transport. The
magnetoresistance measured at T = 4.2 K is negative, increases significantly
with decreasing graphene shell thickness, and is approximated by a formula for
the case of weak localization with a good accuracy. The phase coherence lengths
are in a reasonable relation with the graphene grain sizes. The conducting
aerogels under study complement the well-known set of materials that exhibit
hopping electron transport at low temperatures, which is characteristic of
media with strong carrier localization, and also a negative magnetoresistance,
which usually manifests itself under weak localization conditions.

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The categories of this paper are: hep-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: eess
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The categories of this paper are: physics
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: supr-con