26,480 research outputs found
Dynamical mean-field theories of correlation and disorder
We provide a review of recently-develop dynamical mean-field theory (DMFT)
approaches to the general problem of strongly correlated electronic systems
with disorder. We first describe the standard DMFT approach, which is exact in
the limit of large coordination, and explain why in its simplest form it cannot
capture either Anderson localization or the glassy behavior of electrons.
Various extensions of DMFT are then described, including statistical DMFT,
typical medium theory, and extended DMFT, methods specifically designed to
overcome the limitations of the original formulation. We provide an overview of
the results obtained using these approaches, including the formation of
electronic Griffiths phases, the self-organized criticality of the Coulomb
glass, and the two-fluid behavior near Mott-Anderson transitions. Finally, we
outline research directions that may provide a route to bridge the gap between
the DMFT-based theories and the complementary diffusion-mode approaches to the
metal-insulator transition.Comment: 78 pages, 19 figures; To be published in "Conductor Insulator Quantum
Phase Transitions", edited by V. Dobrosavljevic, N. Trivedi, and J.M. Valles
Jr., Oxford University Press, 2013, ISBN 978019959259
Phase Diagram of the Two-Leg Kondo Ladder
The phase diagram of the two-leg Kondo ladder is investigated using
computational techniques. Ferromagnetism is present, but only at small
conduction electron densities and robust Kondo coupling . For densities
and any Kondo coupling, a paramagnetic phase is found. We also
observed spin dimerization at densities =1/4 and =1/2. The spin structure
factor at small peaks at = for , and at
= for . The charge structure factor suggests
that electrons behave as free particles with spin-1/2 (spin-0) for small
(large) .Comment: 5 pages, 4 fig
Research Report - October 2009. Elaboration of the Module: Definition of the Programme
Alternative innovative didactic methodology is needed to reduce premature school drop out,particularly of young people at risk of exclusion, such as migrants, ethnic groups and children/teenagers from difficult socio-economic background). The key point is to modify the way to deliver learning. Cultural enrichment through young interestas such as music and art, use of technologies, social competencies, problem-solving skills incomputer science, autonomy and sense of purpose may help childhood and adolescence to achieve an improved engagement in school and a sense of educational accomplishmen
Disorder-Driven Non-Fermi Liquid Behavior of Correlated Electrons
Systematic deviations from standard Fermi-liquid behavior have been widely
observed and documented in several classes of strongly correlated metals. For
many of these systems, mounting evidence is emerging that the anomalous
behavior is most likely triggered by the interplay of quenched disorder and
strong electronic correlations. In this review, we present a broad overview of
such disorder-driven non-Fermi-liquid behavior, and discuss various examples
where the anomalies have been studied in detail. We describe both their
phenomenological aspects as observed in experiment, and the current theoretical
scenarios that attempt to unravel their microscopic origin.Comment: Final version, as published in the Reports on Progress in Physic
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