David Logan

Abstract:

The possible nature of the composition induced transition from superconductor to semiconductor in a system with obvious crystalline order - in association with equally obvious electronic disorder - is considered. Topics discussed include: structural parameters, superconductivity, IR spectra, the nature of superconductor-semiconductor transition, as well as percolation and disproportionation.

Abstract:

High resolution electron microscopy of very small (ca. 40 Å diameter) colloidal silver particles established their decahedral morphology.

Abstract:

A simple theory is developed to describe the interplay between Anderson localization and dephasing mechanisms (such as inelastic electron- or exciton-phonon coupling), within the framework of a tight-binding model of spatially disordered systems. Self-consistency is enforced by demanding that only the most probable value of the imaginary part of the site self-energy be self-consistently determined. Dephasing interactions are characterized simply by an energy-independent dephasing rate. When the dephasing rate vanishes the pure localization problem may be examined as the transition is approached from either the localized or the extended regimes; mobility-edge trajectories may thereby be located. In the limit of rapid dephasing the theory correlates with the usual master-equation treatments of incoherent transport. For sufficiently large disorder a nonmonotonic but continuous crossover from coherent to incoherent transport is in general predicted. The problem of Mooij correlation, viewed as a weak-delocalization phenomenon, is also examined: it is suggested that the correlation is not universal as has frequently been supposed. © 1987 The American Physical Society.