Electron Transport in Correlated Low-Dimensional Systems

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9812422 Phillips This is a theoretical grant funded jointly by the Divisions of Materials Research and Chemistry. The research focuses on three topics: the unusual phase transition in the dilute two-dimensional electron gas; transport in electrides; and, disorder in the Kondo effect. When electrons are confined to move in a plane, localization as well as electron correlations are enhanced. This grant focuses on three distinct physical realizations of spatially confined electron systems in which the transport properties are fundamentally linked to localization, electron interaction, or an interplay between the two. In the first system, the focus is on the recent experiments of Kravchenko and colleagues which provide convincing evidence for the existence of a conducting state in a dilute 2D electron gas. These experiments are surprising as it had been previously thought that disorder precludes the presence of metallic conduction in 2D. In this work, the possibility that the experimentally-observed transition corresponds to the melting of a Wigner crystal is explored. We propose that when a Wigner crystal melts, the melted liquid state superconducts. A series of analytical and numerical approaches are discussed to test this proposal. In the second problem, we focus on the interplay between magnetism and disorder in the electride conductor K +(cryptand 2.2.2 )e -. Electrides are a class of organic conductors in which the anion is an electron. The key features that lead to the complexity of the transport and magnetic proerties of this system are the presence of spin singlet electron pairs localized in cavities without the concomitant spin gap, but instead a surprising charge gap. We argue that a model with long range magnetic interactions can explain the transport properties of this system. Finally, experiments by Giordano and co-workers show that in thin metallic films, weak-localization physics can couple to Kondo spin-flip scattering. A scaling an alysis as well as a calculation of the magnetoresistance will be done as extensions of previous work on the feedback effect played by non-magnetic scattering on the Kondo effect. %%% This is a theoretical grant funded jointly by the Divisions of Materials Research and Chemistry. The research focuses on three topics: the unusual phase transition in the dilute two-dimensional electron gas; transport in electrides; and, disorder in the Kondo effect. All three problems have in common the competition between electron interactions and the confinement of electrons to one-and two-dimensional systems. ***