Landau-fluid simulations of Alfvén-wave instabilities in a warm collisionless plasma

A dispersive Landau-fluid model is used to study the decay and modulational instabilities of circularly-polarized Alfvén waves in a collisionless plasma, as well as their nonlinear developments. Comparisons are presented with the drift-kinetic approximation for the dispersionless regime and with hybrid simulations in more general conditions. The effect of the nature of the instability on particle heating is discussed, together with the formation of coherent structures or the development of an inverse cascade

Optical properties of BiTeBr and BiTeCl

We present a comparative study of the optical properties - reflectance, transmission and optical conductivity - and Raman spectra of two layered bismuth-tellurohalides BiTeBr and BiTeCl at 300 K and 5 K, for light polarized in the a-b planes. Despite different space groups, the optical properties of the two compounds are very similar. Both materials are doped semiconductors, with the absorption edge above the optical gap which is lower in BiTeBr (0.62 eV) than in BiTeCl (0.77 eV). The same Rashba splitting is observed in the two materials. A non-Drude free carrier contribution in the optical conductivity, as well as three Raman and two infrared phonon modes, are observed in each compound. There is a dramatic difference in the highest infrared phonon intensity for the two compounds, and a difference in the doping levels. Aspects of the strong electron-phonon interaction are identified. Several interband transitions are assigned, among them the low-lying absorption $\beta$ which has the same value 0.25 eV in both compounds, and is caused by the Rashba spin splitting of the conduction band. An additional weak transition is found in BiTeCl, caused by the lower crystal symmetry.Comment: Accepted in PR

Unusual Shubnikov-de Haas oscillations in BiTeCl

We report measurements of Shubnikov-de Haas (SdH) oscillations in single crystals of BiTeCl at magnetic fields up to 31 T and at temperatures as low as 0.4 K. Two oscillation frequencies were resolved at the lowest temperatures, $F_{1}=65 \pm 4$ Tesla and $F_{2}=156 \pm 5$ Tesla. We also measured the infrared optical reflectance $\left(\cal R(\omega)\right)$ and Hall effect; we propose that the two frequencies correspond respectively to the inner and outer Fermi sheets of the Rashba spin-split bulk conduction band. The bulk carrier concentration was $n_{e}\approx1\times10^{19}$ cm$^{-3}$ and the effective masses $m_{1}^{*}=0.20 m_{0}$ for the inner and $m_{2}^{*}=0.27 m_{0}$ for the outer sheet. Surprisingly, despite its low effective mass, we found that the amplitude of $F_{2}$ is very rapidly suppressed with increasing temperature, being almost undetectable above $T\approx4$ K

Universal response of the type-II Weyl semimetals phase diagram

The discovery of Weyl semimetals represents a significant advance in topological band theory. They paradigmatically enlarged the classification of topological materials to gapless systems while simultaneously providing experimental evidence for the long-sought Weyl fermions. Beyond fundamental relevance, their high mobility, strong magnetoresistance, and the possible existence of even more exotic effects, such as the chiral anomaly, make Weyl semimetals a promising platform to develop radically new technology. Fully exploiting their potential requires going beyond the mere identification of materials and calls for a detailed characterization of their functional response, which is severely complicated by the coexistence of surface- and bulk-derived topologically protected quasiparticles, i.e., Fermi arcs and Weyl points, respectively. Here, we focus on the type-II Weyl semimetal class where we find a stoichiometry-dependent phase transition from a trivial to a non-trivial regime. By exploring the two extreme cases of the phase diagram, we demonstrate the existence of a universal response of both surface and bulk states to perturbations. We show that quasi-particle interference patterns originate from scattering events among surface arcs. Analysis reveals that topologically non-trivial contributions are strongly suppressed by spin texture. We also show that scattering at localized impurities generate defect-induced quasiparticles sitting close to the Weyl point energy. These give rise to strong peaks in the local density of states, which lift the Weyl node significantly altering the pristine low-energy Weyl spectrum. Visualizing the microscopic response to scattering has important consequences for understanding the unusual transport properties of this class of materials. Overall, our observations provide a unifying picture of the Weyl phase diagram

BiTeCl and BiTeBr: a comparative high-pressure optical study

We here report a detailed high-pressure infrared transmission study of BiTeCl and BiTeBr. We follow the evolution of two band transitions: the optical excitation $\beta$ between two Rashba-split conduction bands, and the absorption $\gamma$ across the band gap. In the low pressure range, $p< 4$~GPa, for both compounds $\beta$ is approximately constant with pressure and $\gamma$ decreases, in agreement with band structure calculations. In BiTeCl, a clear pressure-induced phase transition at 6~GPa leads to a different ground state. For BiTeBr, the pressure evolution is more subtle, and we discuss the possibility of closing and reopening of the band gap. Our data is consistent with a Weyl phase in BiTeBr at 5$-$6~GPa, followed by the onset of a structural phase transition at 7~GPa.Comment: are welcom

Spin-resolved electronic response to the phase transition in MoTe2_2

The semimetal MoTe$_2$ is studied by spin- and angle- resolved photoemission spectroscopy to probe the detailed electronic structure underlying its broad range of response behavior. A novel spin-texture is uncovered in the bulk Fermi surface of the non-centrosymmetric structural phase that is consistent with first-principles calculations. The spin-texture is three-dimensional, both in terms of momentum dependence and spin-orientation, and is not completely suppressed above the centrosymmetry-breaking transition temperature. Two types of surface Fermi arc are found to persist well above the transition temperature. The appearance of a large Fermi arc depends strongly on thermal history, and the electron quasiparticle lifetimes are greatly enhanced in the initial cooling. The results indicate that polar instability with strong electron-lattice interactions exists near the surface when the bulk is largely in a centrosymmetric phase

Adherence: a review of education, research, practice and policy in Switzerland.

Nonadherence to medication treatment regimens is a major preventable risk behavior in both acute and chronic diseases. Community pharmacists are facilitators in community care for promoting medication adherence and they should implement interdisciplinary medication adherence programs. To do so, pharmacists should be educated in medication adherence, and new pharmaceutical care policies should be implemented. The healthcare system should evolve to better meet the specific needs of patients. this article describes what has been undertaken in the last decade in medication adherence in terms of education, research, practice and policy in Switzerland. Medline was searched, with the search limited to Switzerland. The three Swiss pharmacy schools were also contacted to collect information about the medication adherence content of both their courses and research programs. National policies related to medication adherence were also reviewed for relevant content. two pharmacy schools offer courses devoted specifically to medication adherence. The number of hours dedicated to the topic varies between 4 to13. a total of 16 studies met the inclusion criteria. Chronic patients were the focus of 9 studies. Medication adherence was the primary outcome of all studies; 10 studies also measured clinical outcomes. Nine studies evaluated the prevalence of medication nonadherence; three studies evaluated the feasibility of new technologies for monitoring adherence; three studies evaluated medication adherence enhancing programs. Policies: three cognitive pharmaceutical services are reimbursed by healthcare insurers, which are directly related to medication adherence. Pharmacists in Switzerland have been actively involved in medication adherence research since the mid '90s. Specific medication adherence courses have entered the curriculum of pharmacy schools, and policies in Switzerland are slowly beginning to meet needs of chronic patients by the introduction of pharmaceutical cognitive services and reimbursement fees

The Presence of Human Immunodeficiency Virus-Associated Neurocognitive Disorders Is Associated With a Lower Adherence to Combined Antiretroviral Treatment.

Human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) are defined according to their diagnostic degrees as follows: asymptomatic neurocognitive impairment, mild neurocognitive disorder, and HIV-associated dementia. Because high adherence to combined antiretroviral therapy (cART) is required to maintain viral suppression among HIV-infected patients, it is important to investigate the impact of HAND on medication adherence. Our study hypothesis was that patients with HAND had a lower medication adherence than patients who did not have HAND. This was an observational, exploratory, 2-center pilot study of patients who had a state-of-the-art neurocognitive assessment performed between January 2011 and June 2015 while also being followed at their respective adherence clinics. Adherence was measured with electronic monitors. Patients' sociodemographic characteristics, HIV viral load, and CD4 counts were retrieved from the Swiss HIV Cohort Study database. At each time t, adherence was computed as the proportion of patients taking medication as prescribed at that time. We included 59 patients, with a median (Q1, Q3) age of 53 years (47-58) and 39 (66%) were male participants. Twenty-two patients (35%) had no neurocognitive deficits, 16 (27%) patients had HAND, and 21 (35%) patients had non-HAND (mostly depression). Implementation over 3 years showed a significant decline (50%) in medication adherence among patients diagnosed with HAND in comparison with patients who had a normal neuropsychological status or a non-HIV-related cognitive deficit (implementation stayed 90% during follow-up). Our findings support the hypothesis that HAND is associated with reduced cART adherence

Micromorph tandem solar cells grown at high rate with in-situ intermediate reflector in industrial KAI PECVD reactors

We report on the latest results of tandem micromorph (a-Si:H/μc-Si:H) silicon solar cells fabricated in commercial Oerlikon Solar KAI-S and KAI-M PECVD reactors. First developments of in-situ silicon oxide based intermediate reflector (SOIR) in KAI reactors are as well presented. Under low depletion conditions (silane concentration 1cm2, with a deposition rate of 0.55 nm/s for microcrystalline silicon and an ex-situ silicon oxide-based intermediate reflector (SOIR). Under high depletion conditions, the growth rate could be raised up to 1.2 nm/s, in a modified KAI-M reactor, and the highest initial efficiency reached so far is 9.7% with in-situ SOIR and top cell thickness of ∼ 230 nm. Promising micromorph solar cells are thus produced under conditions that are highly favorable to low-cost fabrication of tandem modules at an industrial level