Field-induced ultrafast modulation of Rashba coupling at room temperature in ferroelectric α\alpha-GeTe(111)

Rashba materials have appeared as an ideal playground for spin-to-charge conversion in prototype spintronics devices. Among them, $\alpha$-GeTe(111) is a non-centrosymmetric ferroelectric (FE) semiconductor for which a strong spin-orbit interaction gives rise to giant Rashba coupling. Its room temperature ferroelectricity was recently demonstrated as a route towards a new type of highly energy-efficient non-volatile memory device based on switchable polarization. Currently based on the application of an electric field, the writing and reading processes could be outperformed by the use of femtosecond (fs) light pulses requiring exploration of the possible control of ferroelectricity on this timescale. Here, we probe the room temperature transient dynamics of the electronic band structure of $\alpha$-GeTe(111) using time and angle-resolved photoemission spectroscopy (tr-ARPES). Our experiments reveal an ultrafast modulation of the Rashba coupling mediated on the fs timescale by a surface photovoltage (SPV), namely an increase corresponding to a 13 % enhancement of the lattice distortion. This opens the route for the control of the FE polarization in $\alpha$-GeTe(111) and FE semiconducting materials in quantum heterostructures.Comment: 31 pages, 12 figure

A randomized controlled trial of allopurinol in patients with peripheral arterial disease

AbstractBackgroundPatients with peripheral arterial disease (PAD) are limited by intermittent claudication in the distance they can walk. Allopurinol has been shown in coronary arterial disease to prolong exercise before angina occurs, likely by prevention of oxygen wastage in tissues and reduction of harmful oxidative stress.MethodsIn this study we evaluated whether allopurinol could prolong the time to development of leg pain in participants with PAD. In a double-blind, randomized controlled clinical trial participants were randomized to receive either allopurinol 300 mg twice daily or placebo for 6 months. The primary outcome was change in exercise capacity on treadmill testing at 6 months. Secondary outcomes were 6-minute walking distance, Walking Impairment Questionnaire, SF-36 questionnaire, flow-mediated dilatation, and oxidized low-density lipoprotein. Outcome measures were repeated midstudy and at the end of study. The mean age of the 50 participants was 68.4 ± 1.2 years with 39 of 50 (78%) male.ResultsFive participants withdrew during the study (2 active, 3 placebo). There was a significant reduction in uric acid levels in those who received active treatment of 52.1% (P < 0.001), but no significant change in either the pain-free or the maximum walking distance. Other measures of exercise capacity, blood vessel function, and the participants' own assessment of their health and walking ability also did not change during the course of the study.ConclusionsAlthough allopurinol has been shown to be of benefit in a number of other diseases, in this study there was no evidence of any improvement after treatment in patients with PAD

Antigen-Adjuvant Interactions in Vaccines by Taylor Dispersion Analysis: Size Characterization and Binding Parameters

International audienceVaccine adjuvants are immunostimulatory substances used to improve and modulate the immune response induced by antigens. A better understanding of the antigen-adjuvant interactions is necessary to develop future effective vaccine. In this study, Taylor dispersion analysis (TDA) was successfully implemented to characterize the interactions between a polymeric adjuvant (poly(acrylic acid), SPA09) and a vaccine antigen in development for the treatment of Staphylococcus aureus. TDA allowed one to rapidly determine both (i) the size of the antigen-adjuvant complexes under physiological conditions and (ii) the percentage of free antigen in the adjuvant/antigen mixture at equilibrium and finally get the interaction parameters (stoichiometry and binding constant). The complex sizes obtained by TDA were compared to the results obtained by transmission electron microscopy, and the binding parameters were compared to results previously obtained by frontal analysis continuous capillary electrophoresis

Quasi 1D structures at the Bi/InAs(100) surface

APCOM2018 - 24th International conference Applied Physics of Condensed Matter, Štrbské Pleso, Slovaquie, 20 to 22/06/2018"Solid State Physics and Radioactive Irradiation"International audienceThin Bi films are interesting candidates for spintronic applications due to a large spin-orbit splitting that, combined with the loss of inversion symmetry at the surface, results in a band structure that is not spin-degenerate. In recent years, applications for topological insulators based on Bi and Bi alloys have as well attracted much attention. Here we present angle-resolved photoemission spectroscopy studies of the Bi/InAs(100) interface. Bismuth deposition followed by annealing of the surface results in the formation of one full Bi monolayer decorated by Bi nanolines. We found that the building up of the interface does not affect the electronic structure of the substrate. As a consequence of weak interaction, Bi states are placed in the gaps of the electronic structure of InAs(100). We observe a strong resonance of the Bi electronic states close to the Fermi level; its intensity depends on the photon energy and the photon polarization. These states show nearly no dispersion when measured perpendicular to the nanolines, confirming their onedimensionality

Quasi 1D structures at the Bi/InAs(100) surface

APCOM2018 - 24th International conference Applied Physics of Condensed Matter, Štrbské Pleso, Slovaquie, 20 to 22/06/2018"Solid State Physics and Radioactive Irradiation"International audienceThin Bi films are interesting candidates for spintronic applications due to a large spin-orbit splitting that, combined with the loss of inversion symmetry at the surface, results in a band structure that is not spin-degenerate. In recent years, applications for topological insulators based on Bi and Bi alloys have as well attracted much attention. Here we present angle-resolved photoemission spectroscopy studies of the Bi/InAs(100) interface. Bismuth deposition followed by annealing of the surface results in the formation of one full Bi monolayer decorated by Bi nanolines. We found that the building up of the interface does not affect the electronic structure of the substrate. As a consequence of weak interaction, Bi states are placed in the gaps of the electronic structure of InAs(100). We observe a strong resonance of the Bi electronic states close to the Fermi level; its intensity depends on the photon energy and the photon polarization. These states show nearly no dispersion when measured perpendicular to the nanolines, confirming their onedimensionality

Electronic structure of vicinal surfaces tudied by ARPES: case of InAs(111)

International audienceAtomic staircases are among the simplest lateral nanostructures. In particular, electrons belonging to Shockley states of (111)-oriented noble metal surfaces are excellent test systems to explore the basic electronic properties in onedimensional superlattices by means of angular photoemission (ARPES) . These surfaces are characterized by strong emissions from free-electron-like surface states that scatter at step edges.The scattering of electrons at surface defects, such as atomic and molecular adsorbates and monatomic steps, has been made widely popular by scanning tunnelling microscopy (STM) . Observed interference patterns mirror fundamental properties of solid crystals related to electron transport and quantum confinement, such as the inelastic lifetime and quantum coherence of a scattered electron. However, even at noble metal surfaces, considered as model systems, the nature of the step potential is more complex and fundamental questions remain open . InAs(111) A and B surfaces are known to support a two-dimensional electron gas (2DEG) exhibiting a multitude of fundamental physical phenomena that can be of major importance for technological applications. The 2DEG, observed for the first time by Olsson et al. is related to the charge accumulation layer induced by band bending. We have investigated by ARPES the electronic structure of the InAs(111) prepared by molecular beam epitaxy (MBE). On InAs(111)-B we obtained a large splitting in the 2DEG than cannot be explained by the Rashba or Dresselhaus effects. STM images on the MBE prepared surface show array of equally spaced, monatomic, parallel steps. So, the 2DEG splitting can be attributed to the superlattice band folding depending on the step lattice constan

Proposition de document de cadrage Évaluation environnementale de projets impliquant des méthodes d'IA

L'objectif de ce document est de fournir des critères pour l'évaluation des impacts environnementaux des réponses aux appels à projet impliquant des méthodes d'Intelligence Artificielle (IA). Lors de la proposition de ces critères, nous prenons en compte, en plus des impacts généraux des services numériques, les spécificités du domaine de l'IA et en particulier de l'apprentissage automatique : impacts des phases d'apprentissage et d'inférence, collecte des données..

Proposition de document de cadrage Évaluation environnementale de projets impliquant des méthodes d'IA

L'objectif de ce document est de fournir des critères pour l'évaluation des impacts environnementaux des réponses aux appels à projet impliquant des méthodes d'Intelligence Artificielle (IA). Lors de la proposition de ces critères, nous prenons en compte, en plus des impacts généraux des services numériques, les spécificités du domaine de l'IA et en particulier de l'apprentissage automatique : impacts des phases d'apprentissage et d'inférence, collecte des données..