Strong negative magnetoresistance and hopping transport in graphenized nematic aerogels

TL;DR

This study investigates the magnetoresistance and transport mechanisms in nematic aerogels coated with graphene, revealing weak localization effects, electron-electron interactions, and hopping transport depending on carbon content.

Contribution

It provides new insights into the magnetotransport properties of graphenized nematic aerogels, highlighting the transition from weak localization to hopping mechanisms with varying carbon content.

Findings

Negative magnetoresistance consistent with weak localization

Transition from two-dimensional to one-dimensional localization at low temperatures

Hopping transport observed in low carbon content samples

Abstract

The transport properties of nematic aerogels, which consist of oriented mullite nanofibers coated with a graphene shell, were studied. It is shown that the magnetoresistance of this system is well approximated by two contributions - negative one, described by the formula for systems with weak localization , and positive contribution, linear in the field and unsaturated in large magnetic fields. The behavior of phase coherence length on temperature obtained from the analysis of the negative contribution indicates the main role of the electron-electron interaction in the destruction of phase coherence and, presumably, the transition at low temperatures from a two-dimensional weak localization regime to a one-dimensional one. The positive linear contribution to magnetoresistance is apparently due to the inhomogeneous distribution of the local carrier density in the conductive medium. It has also been established that the temperature dependence of the resistance for graphenized aerogels with a low carbon content, when the graphene coating is apparently incomplete, can be represented as the sum of two contributions, one of which is characteristic of weak localization, and the second is described by hopping mechanism corresponding to the Shklovskii-Efros law in the case of a granular conductive medium. For samples with a high carbon content, there is no second contribution.