Weak localization and coulomb interaction in graphite intercalation compounds and related materials
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Weak localization and coulomb interaction in graphite intercalation compounds and related materials L. Pirauxa) Unite de Physico-Chimie et de Physique des Materiaux, Universite Catholique de Louvain, place Croix du Sud 1, B-1348 Louvain-la-Neuve, Belgium (Received 8 December 1989; accepted 21 February 1990)
The effects of weak-localization and electron-electron interaction have to be invoked to explain anomalies in the resistivity and the magnetoresistance of quasi two-dimensional electron systems formed in acceptor graphite intercalation compounds and in pregraphitic carbon materials. After introducing the basic concepts involved in the physics of these phenomena, a review is given of recent data for the low temperature electronic transport properties in these materials. I. INTRODUCTION
In the usual Boltzmann theory of transport, the low-temperature resistivity of a weakly disordered metallic system is traditionally written as the sum of two terms P(T) = po + AT" (1) where po is the temperature-independent residual resistivity due to static imperfections, such as impurities, while the temperature-dependent term is due to electron-phonon or electron-electron collisions. Weak disorder means that the mean free path l0 is much greater than the average atomic distance a ~ kv~l in metals; i.e., kFl0 t> 1 where kF is the Fermi wave vector. As in the above expression bothyl and the exponent n are positive; dp/dT is also positive. In the last decade, experimental investigations of the low-temperature resistivity of a variety of weakly disordered electron systems have led to the observation of an increasing resistance as the temperature is lowered (dp/dT < 0), implying that the Boltzmann theory no longer constitutes a good approximation for treating the motion of the charge carriers. It was found that the corrections become more and more important as the temperature approaches zero and as the amount of disorder increases. If such deviations from the Boltzmann theory exist in one- , two- , and three-dimensional systems as well, it follows that the magnitude of the effect as well as the resistivity behavior as a function of temperature depend strongly on the dimensionality of the system. In fact, the corrections are larger in systems of lower dimensionality, while in the particular case of "'Research Associate of the National Fund for Scientific Research (Belgium).
J. Mater. Res., Vol. 5, No. 6, Jun 1990
http://journals.cambridge.org
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quasi two-dimensional systems, the resistivity increases logarithmically with decreasing temperature. This nonclassical aspect of the carrier transport has been theoretically interpreted in terms of two distinct mechanisms: weak localization and electron-electron interaction. In the next section, we will briefly discuss the basic ideas and the theoretical relations involved in these quantum phenomena including multiple scattering and interference. For a more comprehensive and detailed treatment of this field, Refs. 1-4 should be consulted. The purpose of this review
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