Moving Dirac nodes by chemical substitution.

Dirac fermions play a central role in the study of topological phases, for they can generate a variety of exotic states, such as Weyl semimetals and topological insulators. The control and manipulation of Dirac fermions constitute a fundamental step toward the realization of novel concepts of electronic devices and quantum computation. By means of Angle-Resolved Photo-Emission Spectroscopy (ARPES) experiments and ab initio simulations, here, we show that Dirac states can be effectively tuned by doping a transition metal sulfide, [Formula: see text], through Co/Ni substitution. The symmetry and chemical characteristics of this material, combined with the modification of the charge-transfer gap of [Formula: see text] across its phase diagram, lead to the formation of Dirac lines, whose position in k-space can be displaced along the [Formula: see text] symmetry direction and their form reshaped. Not only does the doping x tailor the location and shape of the Dirac bands, but it also controls the metal-insulator transition in the same compound, making [Formula: see text] a model system to functionalize Dirac materials by varying the strength of electron correlations.

Unidirectional Rashba spin splitting in single layer WS2(1-x)Se2xalloy.

Atomically thin two-dimensional (2D) layered semiconductors such as transition metal dichalcogenides have attracted considerable attention due to their tunable band gap, intriguing spin-valley physics, piezoelectric effects and potential device applications. Here we study the electronic properties of a single layer WS1.4Se0.6alloys. The electronic structure of this alloy, explored using angle resolved photoemission spectroscopy, shows a clear valence band structure anisotropy characterized by two paraboloids shifted in one direction of thek-space by a constant in-plane vector. This band splitting is a signature of a unidirectional Rashba spin splitting with a related giant Rashba parameter of 2.8 ± 0.7 eV Å. The combination of angle resolved photoemission spectroscopy with piezo force microscopy highlights the link between this giant unidirectional Rashba spin splitting and an in-plane polarization present in the alloy. These peculiar anisotropic properties of the WS1.4Se0.6alloy can be related to local atomic orders induced during the growth process due the different size and electronegativity between S and Se atoms. This distorted crystal structure combined to the observed macroscopic tensile strain, as evidenced by photoluminescence, displays electric dipoles with a strong in-plane component, as shown by piezoelectric microscopy. The interplay between semiconducting properties, in-plane spontaneous polarization and giant out-of-plane Rashba spin-splitting in this 2D material has potential for a wide range of applications in next-generation electronics, piezotronics and spintronics devices.

Hybridization and localized flat band in the WSe2/MoSe2heterobilayer.

Nearly localized moiré flat bands in momentum space, arising at particular twist angles, are the key to achieve correlated effects in transition-metal dichalcogenides. Here, we use angle-resolved photoemission spectroscopy (ARPES) to visualize the presence of a flat band near the Fermi level of van der Waals WSe2/MoSe2heterobilayer grown by molecular beam epitaxy. This flat band is localized near the Fermi level and has a width of several hundred meVs. By combining ARPES measurements with density functional theory calculations, we confirm the coexistence of different domains, namely the reference 2H stacking without layer misorientation and regions with arbitrary twist angles. For the 2H-stacked heterobilayer, our ARPES results show strong interlayer hybridization effects, further confirmed by complementary micro- Raman spectroscopy measurements. The spin-splitting of the valence band atKis determined to be 470 meV. The valence band maximum (VBM) position of the heterobilayer is located at the Γ point. The energy difference between the VBM at Γ and theKpoint is of -60 meV, which is a stark difference compared to individual single monolayer WSe2and monolayer WSe2, showing both a VBM atK.

Manipulating the Topological Interface by Molecular Adsorbates: Adsorption of Co-Phthalocyanine on Bi2Se3.

Topological insulators are a promising class of materials for applications in the field of spintronics. New perspectives in this field can arise from interfacing metal-organic molecules with the topological insulator spin-momentum locked surface states, which can be perturbed enhancing or suppressing spintronics-relevant properties such as spin coherence. Here we show results from an angle-resolved photemission spectroscopy (ARPES) and scanning tunnelling microscopy (STM) study of the prototypical cobalt phthalocyanine (CoPc)/Bi2Se3 interface. We demonstrate that that the hybrid interface can act on the topological protection of the surface and bury the Dirac cone below the first quintuple layer.

[Palliative care in Lebanon: views of health professionals and relatives]. / Soins palliatifs au Liban: Avis des soignants et des proches.

CONTEXT: The development of palliative care is still in its primitive state in Lebanon and few studies assessed the views of caregivers on the quality of support of their patients and the difficulties they encounter. We evaluate the perspective of caregivers and the relatives in regard to the quality of support to the terminally ill patients. METHOD: A cross-sectional descriptive, analytic and comparative study is carried out between September and October 2010, among two groups - Group 1: Health professionals from a university hospital in Beirut; Group 2 : Relatives of recently deceased persons following a chronic, incurable disease. RESULTS: We received 447 responses: 358 in the hospital from caregivers (80%) and 89 in the city from relatives (20%). The management of physical problems of patients at end of life is considered adequate by 68% of caregivers while only 40% believe that psychological problems are managed adequatly. Physical difficulties most often encountered are intractable pain (44%) ; psychological problems frequently noted at this stage are depression (40%), anxiety (18%) and fear of death (115%). Caregivers (69%) and relatives (62%) are in favor of informing the patient about the seriousness of his illness; and physicians more frequently than nurses (75% vs 675%, p = 0.002). Relatives (75%) and caregivers (73%) believe that today in Lebanon, the terminally ill patients do not die in peace and dignity (p = 0.022). 71% of caregivers vs 62% of relatives consider that intensive medications are used in cancer patients (p < 0.001) and non-cancer patients (61% caregivers vs 60% of relatives; p > 0.05). CONCLUSION: The management of terminally ill patients and their families must be improved. Palliative care services adapted to the cultural, social and economic characteristics of the country, and involving the private and public sectors should be integrated into the current health system.

High p doped and robust band structure in Mg-doped hexagonal boron nitride.

In two dimensional materials, substitutional doping during growth can be used to alter the electronic properties. Here, we report on the stable growth of p-type hexagonal boron nitride (h-BN) using Mg-atoms as substitutional impurities in the h-BN honeycomb lattice. We use micro-Raman spectroscopy, angle-resolved photoemission measurements (nano-ARPES) and Kelvin probe force microscopy (KPFM) to study the electronic properties of Mg-doped h-BN grown by solidification from a ternary Mg-B-N system. Besides the observation of a new Raman line at ∼1347 cm-1 in Mg-doped h-BN, nano-ARPES reveals p-type carrier concentration. Our nano-ARPES experiments demonstrate that the Mg dopants can significantly alter the electronic properties of h-BN by shifting the valence band maximum about 150 meV toward higher binding energies with respect to pristine h-BN. We further show that, Mg doped h-BN exhibits a robust, almost unaltered, band structure compared to pristine h-BN, with no significant deformation. Kelvin probe force microscopy (KPFM) confirms the p-type doping, with a reduced Fermi level difference between pristine and Mg-doped h-BN crystals. Our findings demonstrate that conventional semiconductor doping by Mg as substitutional impurities is a promising route to high-quality p-type doped h-BN films. Such stable p-type doping of large band h-BN is a key feature for 2D materials applications in deep ultra-violet light emitting diodes or wide bandgap optoelectronic devices.

Strain and Spin-Orbit Coupling Engineering in Twisted WS2/Graphene Heterobilayer.

The strain in hybrid van der Waals heterostructures, made of two distinct two-dimensional van der Waals materials, offers an interesting handle on their corresponding electronic band structure. Such strain can be engineered by changing the relative crystallographic orientation between the constitutive monolayers, notably, the angular misorientation, also known as the "twist angle". By combining angle-resolved photoemission spectroscopy with density functional theory calculations, we investigate here the band structure of the WS2/graphene heterobilayer for various twist angles. Despite the relatively weak coupling between WS2 and graphene, we demonstrate that the resulting strain quantitatively affects many electronic features of the WS2 monolayers, including the spin-orbit coupling strength. In particular, we show that the WS2 spin-orbit splitting of the valence band maximum at K can be tuned from 430 to 460 meV. Our findings open perspectives in controlling the band dispersion of van der Waals materials.

Phase Transition in a Memristive Suspended MoS2 Monolayer Probed by Opto- and Electro-Mechanics.

Semiconducting monolayers of a 2D material are able to concatenate multiple interesting properties into a single component. Here, by combining opto-mechanical and electronic measurements, we demonstrate the presence of a partial 2H-1T' phase transition in a suspended 2D monolayer membrane of MoS2. Electronic transport shows unexpected memristive properties in the MoS2 membrane, in the absence of any external dopants. A strong mechanical softening of the membrane is measured concurrently and may only be related to the 2H-1T' phase transition, which imposes a 3% directional elongation of the topological 1T' phase with respect to the semiconducting 2H. We note that only a few percent 2H-1T' phase switching is sufficient to observe measurable memristive effects. Our experimental results combined with first-principles total energy calculations indicate that sulfur vacancy diffusion plays a key role in the initial nucleation of the phase transition. Our study clearly shows that nanomechanics represents an ultrasensitive technique to probe the crystal phase transition in 2D materials or thin membranes. Finally, a better control of the microscopic mechanisms responsible for the observed memristive effect in MoS2 is important for the implementation of future devices.

Real-world Management of Women with Postmenopausal Osteoporosis Treated with Denosumab: A Prospective Observational Study in the Czech Republic and Slovakia.

INTRODUCTION: Osteoporosis is characterized by low bone mineral density (BMD) and an increased risk of fracture. In randomized controlled trials, denosumab has been shown to significantly reduce the fracture risk in women with osteoporosis. However, little is known about the real-world management of women who are prescribed denosumab. METHODS: This multicenter, prospective, observational real-world study in the Czech Republic and Slovakia evaluated the baseline characteristics and clinical management of women with postmenopausal osteoporosis prescribed denosumab for 24 months. RESULTS: A total of 600 women were included (300 in each country). In the Czech Republic and Slovakia, respectively, mean age at enrollment was 69.0 and 64.3 years, 67.7% and 30.0% of patients had a previous osteoporotic fracture, and 85.0% and 48.7% had previously received osteoporosis medication. In both countries, 'low BMD T score' and 'a history of osteoporotic fracture' were the main reasons for prescribing denosumab. Most patients received all four post-baseline denosumab injections (Czech Republic, 82.0%; Slovakia, 81.0%), and more than 98% of patients in both countries received all injections at the prescribing center. At 24 months, most patients experienced an increase in BMD T score for the lumbar spine, total hip, or femoral neck (Czech Republic, 69.7-91.7%; Slovakia, 67.1-92.9%). Adverse drug reactions were consistent with the known safety profile of denosumab. CONCLUSION: Baseline characteristics of patients receiving denosumab in the Czech Republic and Slovakia reflect the reimbursement criteria for this agent in each country. The findings of our study in patients who are at high risk for fracture are consistent with the growing body of evidence demonstrating the effectiveness of denosumab in real-world clinical practice. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT01652690. FUNDING: Amgen Inc.