Activated Hopping Transport in Nematic Conducting Aerogels

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