Metallic and semi-metallic <100> silicon nanowires

Silicon nanowires grown along the -direction with a bulk Si core are studied with density functional calculations. Two surface reconstructions prevail after exploration of a large fraction of the phase space of nanowire reconstructions. Despite their energetical equivalence, one of the reconstructions is found to be strongly metallic while the other one is semi-metallic. This electronic-structure behavior is dictated by the particular surface states of each reconstruction. These results imply that doping is not required in order to obtain good conducting Si nanowires.Comment: 13 pages, 4 figures; Phys. Rev. Lett., in pres

Carrier-envelope phase dependence in single-cycle laser pulse propagation with the inclusion of counter-rotating terms

We focus on the propagation properties of a single-cycle laser pulse through a two-level medium by numerically solving the full-wave Maxwell-Bloch equations. The counter-rotating terms in the spontaneous emission damping are included such that the equations of motion are slightly different from the conventional Bloch equations. The counter-rotating terms can considerably suppress the broadening of the pulse envelope and the decrease of the group velocity rooted from dispersion. Furthermore, for incident single-cycle pulses with envelope area 4$\pi$, the time-delay of the generated soliton pulse from the main pulse depends crucially on the carrier-envelope phase of the incident pulse. This can be utilized to determine the carrier-envelope phase of the single-cycle laser pulse.Comment: 6 pages, 5 figure

Effect of solute content and temperature on the deformation mechanisms and critical resolved shear stress in Mg-Al and Mg-Zn alloys

The influence of solute atoms (Al and Zn) on the deformation mechanisms and the critical resolved shear stress for basal slip in Mg alloys at 298 K and 373 K was ascertained by micropillar compression tests in combination with high-throughput processing techniques based on the diffusion couples. It was found that the presence of solute atoms enhances the size effect at 298 K as well as the localization of deformation in slip bands, which is associated with large strain bursts in the resolved shear stress ($\tau_{RSS}$)-strain ($\epsilon$) curves. Deformation in pure Mg and Mg alloys was more homogeneous at 373 K and the influence of the micropillar size on the critical resolved shear stress was much smaller. In this latter case, it was possible to determine the effect of solute content on the critical resolved shear stress for basal slip in Mg-Al and Mg-Zn alloys

Half-metallicity and efficient spin injection in AlN/GaN:Cr (0001) heterostructure

First-principles investigations of the structural, electronic and magnetic properties of Cr-doped AlN/GaN (0001) heterostructures reveal that Cr segregates into the GaN region, that these interfaces retain their important half-metallic character and thus yield efficient (100 %) spin polarized injection from a ferromagnetic GaN:Cr electrode through an AlN tunnel barrier - whose height and width can be controlled by adjusting the Al concentration in the graded bandgap engineered Al(1-x)Ga(x)N (0001) layers.Comment: submitted for publicatio

Penicillium marneffei infection presenting as vulv-ulcer in an HIV-infected woman

We report the case of an HIV-infected patient with vulv-ulcer as first manifestation associated with Penicillium marneffei, which is of special interest for healthcare workers in all fields

Probing the electronic properties and charge state of gold nanoparticles on ultrathin MgO versus thick doped CaO films

Electron transfer into metal nanoparticles on oxide supports is associated with unusual morphological, electronic, and chemical properties of the charged system. Two fundamental charging routes have been identified so far, which are electron tunneling through ultrathin oxide films supported by a bulk metal and charge donation from single-ion impurities embedded in the oxide matrix. In this study, we have investigated whether both routes lead to the formation of metal deposits with identical properties. For this purpose, Au islands have been prepared on 1−2ML thin MgO/Ag(001) layers and on 25-ML-thick CaO films doped with Mo impurities. The morphological and electronic properties of the islands were analyzed with low-temperature scanning tunneling microscopy (STM) and spectroscopy. In both systems, pronounced electron confinement effects are observed in the nanostructures, arising from the quantization of one and the same Au electronic band. Moreover, clear experimental signatures for a charge transfer into the islands are found, such as a layer-by-layer growth of the ad-metal and a negative contrast of the oxide region around the deposits in STM images. Our data provide evidence that the charged nanostructures exhibit comparable properties independent of the origin of the extra electrons. This agreement suggests that ultrathin oxide films may be used as model systems for doped bulk oxides, as used in heterogeneous catalysis

Spin photocurrent, its spectra dependence, and current-induced spin polarization in an InGaAs/InAlAs two-dimensional electron gas

Converse effect of spin photocurrent and current induced spin polarization are experimentally demonstrated in the same two-dimensional electron gas system with Rashba spin splitting. Their consistency with the strength of the Rashba coupling as measured from beating of the Shubnikov-de Haas oscillations reveals a unified picture for the spin photocurrent, current-induced spin polarization and spin orbit coupling. In addition, the observed spectral inversion of the spin photocurrent indicates the system with dominating structure inversion asymmetry.Comment: 13 pages, 4 figure