Spin polarization of the L-gap surface states on Au(111)

The electron spin polarization (ESP) of the L-gap surface states on Au(111) is investigated theoretically by means of first-principles electronic-structure and photoemission calculations. The surface states show a large spin-orbit induced in-plane ESP which is perpendicular to the in-plane wavevector, in close analogy to a two-dimensional electron gas with Rashba spin-orbit interaction. The surface corrugation leads to a small ESP component normal to the surface, being not reported so far. The surface-states ESP can be probed qualitatively and quantitatively by spin- and angle-resolved photoelectron spectroscopy, provided that the initial-state ESP is retained in the photoemission process and not obscured by spin-orbit induced polarization effects. Relativistic photoemission calculations provide detailed information on what photoemission set-ups allow to conclude from the photoelectron ESP on that of the surface states.Comment: 22 pages with 8 figure

Transport Properties of Holographic Defects

We study the charge transport properties of fields confined to a (2+1)-dimensional defect coupled to (3+1)-dimensional super-Yang-Mills at large-\nc and strong coupling, using AdS/CFT techniques applied to linear response theory. The dual system is described by \nf probe D5- or D7-branes in the gravitational background of \nc black D3-branes. Surprisingly, the transport properties of both defect CFT's are essentially identical -- even though the D7-brane construction breaks all supersymmetries. We find that the system possesses a conduction threshold given by the wave-number of the perturbation and that the charge transport arises from a quasiparticle spectrum which is consistent with an intuitive picture where the defect acquires a finite width. We also examine finite-$\lambda$ modifications arising from higher derivative interactions in the probe brane action.Comment: 54 pages, 22 figures, references added, minor changes to figures and comments, final version published in JHE

Structural Basis of Pattern Recognition by Innate Immune Molecules

The importance of the innate immune system as a first line defence against pathogenic challenge has long been recognised. Over the last decade the identity of many of the key molecules mediating innate host defence have been clarified and a model of self/nonself discrimination by families of pattern recognition receptors (PRRs) has emerged. Although a large amount of information is now available concerning the action of these innate immune molecules at the level of the cell and organism, little is known about the molecular interface between pathogens and innate immune recognition molecules. In this chapter the molecular basis for innate immune discrimination of a wide variety of pathogen derived molecules is discussed in the context of the emerging literature