Tunable spin transport in CrAs: role of correlation effects

Correlation effects on the electronic structure of half-metallic CrAs in zinc-blende structure are studied for different substrate lattice constants. Depending on the substrate the spectral weight of the non-quasiparticle states might be tuned from a well developed value in the case of InAs substrate to an almost negligible contribution for the GaAs one. A piezoelectric material that would allow the change in the substrate lattice parameters opens the possibility for practical investigations of the switchable (tunable) non-quasiparticle states. Since the latter are important for the tunneling magnetoresistance and related phenomena it creates new opportunities in spintronics.Comment: 12 pages, 3 figures, 2 tables. accepted PRB 71, 1 (2005

The Influence of Substrate Structure on Membrane Adhesion

We consider a membrane both weakly and strongly adhering to a geometrically structured substrate. The interaction potential is assumed to be local, via the Deryagin approximation, and harmonic. Consequently, we can analytically describe a variety of different geometries: as well as randomly rough self-affine surfaces, smooth substrates interrupted by an isolated cylindrical pit, a single elongated trench or a periodic array of trenches are investigated. We present more general expressions for the adhesion energy and membrane configuration in Fourier space and find that, compared to planar surfaces, the adhesion energy decreases. We also highlight the possibility of overshoots occurring in the membrane profile and look at its degree of penetration into surface indentations.Comment: 41 pages LaTex, 12 EPS figure

Surface rearrangement at complex adsorbate-substrate interfaces

On the basis of the information theory approach we propose a novel statistical scheme for analyzing the evolution of coupled adsorbate-substrate systems, in which the substrate undergoes the adsorbate-induced transformations. A relation between the substrate morphology and the adsorbate thermodynamic state is established. This allows one to estimate the surface structure in terms of incomplete experimental information and the one concerning the adsorbate thermodynamic response to the structural modifications.Comment: 5 pages, 3 figure

Optimizing electronic structure and quantum transport at the graphene-Si(111) interface: An ab-initio density-functional study

We use ab initio density functional calculations to determine the interaction of a graphene monolayer with the Si(111) surface. We found that graphene forms strong bonds to the bare substrate and accommodates the 12% lattice mismatch by forming a wavy structure consisting of free-standing conductive ridges that are connected by ribbon-shaped regions of graphene, which bond covalently to the substrate. We perform quantum transport calculations for different geometries to study changes in the transport properties of graphene introduced by the wavy structure and bonding to the Si substrate. Our results suggest that wavy graphene combines high mobility along the ridges with efficient carrier injection into Si in the contact regions

Stress relief as the driving force for self-assembled Bi nanolines

Stress resulting from mismatch between a substrate and an adsorbed material has often been thought to be the driving force for the self-assembly of nanoscale structures. Bi nanolines self-assemble on Si(001), and are remarkable for their straightness and length -- they are often more than 400 nm long, and a kink in a nanoline has never been observed. Through electronic structure calculations, we have found an energetically favourable structure for these nanolines that agrees with our scanning tunneling microscopy and photoemission experiments; the structure has an extremely unusual subsurface structure, comprising a double core of 7-membered rings of silicon. Our proposed structure explains all the observed features of the nanolines, and shows that surface stress resulting from the mismatch between the Bi and the Si substrate are responsible for their self-assembly. This has wider implications for the controlled growth of nanostructures on semiconductor surfaces.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let