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The objective of this study is to propose a modelling approach to quantify the contribution of mains coastal catchments of North Africa in sediment and nitrate fluxes to the Mediterranean Sea. We use the Soil and Water Assessment Tool (SWAT) on the biggest coastal rivers, Moulouya (55 860 km2), Tafna (7200 km2), Chelif (44 694 km2) Oued el Kebir (8 824 km2) and Medjerda (23 213 km2). Simulation was performed monthly from 2003 to 2013. The model represents correctly the dynamics of water, sediment and nitrate flux. Rivers carry between 22 .103 to 390 103t yr-1 of sediments and Oued el Kebir contributes with 55% of the total amount, while nitrate fluxes vary from 182 to 1715 t yr-1 and Moulouya contributes with 32% of the total quantity. The simulations show us that the North African dams stocked a large amount of sediment (98%) and nitrates (39%) transported by rivers.

Two-dimensional electron gases (2DEGs) are at the base of current nanoelectronics because of their exceptional mobilities. Often the accumulation layer forms at polar interfaces with longitudinal optical (LO) modes. In most cases, the many-body screening of the quasi-2DEGs dramatically reduces the Fröhlich scattering strength. Despite the effectiveness of such a process, it has been recurrently proposed that a remote coupling with LO phonons persists even at high carrier concentration. We address this issue by perturbing electrons in an accumulation layer via an ultrafast laser pulse and monitoring their relaxation via time- and momentum-resolved spectroscopy. The cooling rate of excited carriers is monitored at doping level spanning from the semiconducting to the metallic limit. We observe that screening of LO phonons is not as efficient as it would be in a strictly 2D system. The large discrepancy is due to the remote coupling of confined states with the bulk. Our data indicate that the effect of such a remote coupling can be mimicked by a 3D Fröhlich interaction with Thomas–Fermi screening. These conclusions are very general and should apply to field effect transistors (FET) with high- [Formula: see text] dielectric gates, van der Waals heterostructures, and metallic interfaces between insulating oxides.

This study investigated temporal changes in the vertical distribution of invertebrates during periods of low flows in the Tafna wadi, a semi-arid Mediterranean river characterised by a general decline in average flows. The hyporheos was sampled along a 130-m stretch at depths of 0.3, 0.6 and 1 m in a pool-riffle sequence and a lateral gravel bar. Benthic fauna was collected on each sampling occasion from different locations in the studied sections. Sampling was conducted in two consecutive years (2014 and 2015) at the end of the spring (high waters) and over a 2-month period during the low summer flow. The results indicated that high surface water temperatures may initiate the movement of some taxa into the interstitial habitat, thus supporting the hyporheic refuge hypothesis. In the hyporheic zone, the low oxygen rates recorded deeper in the sediment and in the last low-flow months caused significant declines in taxonomic richness, and lower pH values resulted in a reduction in invertebrate abundances. In the benthic zone, high flow velocities increased richness but decreased invertebrate abundances. A large number of taxa were found in the gravel bar section reflecting the more suitable living conditions in this habitat compared with the river reach (high DO rates).

Decisions on market authorization (MA) and reimbursement have different durations across countries because of health technology assessment (HTA) procedures and negotiations between manufacturers and national authorities. To overcome this delay, France has implemented a Temporary Authorization for Use (ATU) program that allows early access to drugs before MA, in order to treat patients with unmet medical needs. The objectives of our study were to establish the added therapeutic benefit (ATB) of ATUs for solid tumors and to investigate the correlations between three tools evaluating ATB and survival outcomes and drug costs. Data on ATUs granted from January 2009 to December 2019 to treat solid tumors were analyzed. An assessment of their ATB was conducted using the American Society of Clinical Oncology-Value Framework (ASCO-VF), the European Society for Medical Oncology-Magnitude Clinical Benefit Scale (ESMO-MCBS) and the French HTA criterion, clinical added value (CAV). The latter score determines reimbursement and national market access. Thirty-five drugs in 39 indications were granted ATUs. All of them obtained MA and derived a clinical benefit to be reimbursed by the Social Security. Twenty-eight (71.8%) had CAV compared to preexisting therapies. 24/38 (63.2%) had a 4-5 ESMO-MCBS score and 19/33 (57.6%) had an ASCO-VF score over 45. No correlations were found between cost, PFS, OS, CAV and ASCO-VF score, while high ESMO-MCBS scores were correlated to OS. In conclusion, many patients were treated with innovations before MA thanks to ATU, although there are discrepancies between ATB scales, hence the importance of international collaboration in the evaluation of innovative therapies.

International audience; The large tolerance of hybrid perovksites to the trapping of electrons by defects is a key asset in photovoltaic applications. Here, the ionic surface terminations of CH3NH3PbI3 are employed as a testbed to study the effect of electrostatic fields on the dynamics of excited carriers. We characterize the transition across the tetragonal to orthorhombic phase. The observed type II band offset and drift of the excited electrons highlight the important role that organic cations have on the screening of local electrostatic fields. When the orientation of organic cations is frozen in the orthorhombic phase, the positively charged termination induces a massive accumulation of excited electrons at the surface of the sample. Conversely, no electron accumulation is observed in the tetragonal phase. We conclude that the local fields cannot penetrate in the sample when the polarizability of freely moving cations boosts the dielectric constant up to ϵ = 120.

International audience; Self-assembled nanolines are attractive to build the technological devices of next generation, but characterizing their electronic properties is often difficult to achieve. In this work we employ angle-resolved photoemission spectroscopy and density functional theory to clarify the electronic structure exhibited by self-assembled Bi nanolines grown on the InAs(100) surface. A surface resonance associated to the reconstructed (4 2) surface is visible in the photoemission spectra before and after the formation of the Bi nanolines. This demonstrates that Bi deposition does not necessarily drive a transition to an unreconstructed surface in the substrate, which is contrary to what was reported in previous studies. In addition, experiment and theory show the presence of a flat band located in the band gap of InAs, just above the valence band maximum. This flat band is associated to the Bi nanolines and possesses a strong orbital character, consistent with its unidimensional nature. These spectral features suggest that Bi nanolines on InAs(100) may have a strongly polarized conductivity, which makes them suitable to be exploited as nanowires in nanotechnology. The coexistence with an accumulation layer suggests an even farther functionalization.

In the past decade, tumour flare reaction (TFR) was considered as a new side effect associated with immunomodulatory agents (IMiDs) and as a condition of chronic lymphocytic leukaemia (CLL). However, this phenomenon is also observed with immune checkpoint inhibitors in solid tumours. It is still poorly understood and its incidence is underestimated. TFR has been associated with morbidity, therefore, early recognition and management of patients with TFR is critical. An exhaustive literature research between 1985 and 2016 was performed using PubMed; American Society of Clinical Oncology and American Society of Hematology abstracts reporting TFR or pseudoprogression were identified. The incidence of TFR in CLL ranged from 28 to 58%. Tumour response in patients treated beyond progression was reported in 9.7% with ipilimumab, 10% with nivolumab, 6.7 and 12% with pembrolizumab, and in renal cell carcinoma 69% with nivolumab. Rare life-threatening or fatal cases were reported; symptoms were usually mild. Studies showed that treating patients beyond progression yielded tumour responses, considering TFR as predictive of response. Treatment with immunomodulatory agents is associated with TFR, often misinterpreted as progression. Therefore, the identification of appropriate clinical benefit criteria and the use of immune-related response criteria in prospective trials for a better understanding are compulsory.

International audience; Quasi two-dimensional hybrid organic-inorganic perovskites (HOIPs) have been rediscovered recently for photovoltaics due to a higher stability than other HOIPs. We focus here on the electronic structure of the 2D perovskite (C6H5C2H4NH3)2PbI4. We perform an experimental k-resolved determination of the valence and conduction bands by angle-resolved photoemission spectroscopy (ARPES) and inverse photoemission spectroscopy (IPES). The experimental and theoretical dispersions are compared. The valence band width is in agreement with that of renormalized theoretical bands, while no significative renormalization is observed for the conduction band. The effect of the spin-orbit coupling in the conduction band is also experimentally observed.

The low-energy electronic structure, including the Fermi surface topology, of the itinerant metamagnet $$\hbox {Sr}_{{4}}\hbox {Ru}_{{3}}\hbox {O}_{{10}}$$ Sr 4 Ru 3 O 10 is investigated for the first time by synchrotron-based angle-resolved photoemission. Well-defined quasiparticle band dispersions with matrix element dependencies on photon energy or photon polarization are presented. Four bands crossing the Fermi-level, giving rise to four Fermi surface sheets are resolved; and their complete topography, effective mass as well as their electron and hole character are determined. These data reveal the presence of kink structures in the near-Fermi-level band dispersion, with energies ranging from 30 to 69 meV. Together with previously reported Raman spectroscopy and lattice dynamic calculation studies, the data suggest that these kinks originate from strong electron–phonon coupling present in $$\hbox {Sr}_{{4}}\hbox {Ru}_{{3}}\hbox {O}_{{10}}$$ Sr 4 Ru 3 O 10 . Considering that the kink structures of $$\hbox {Sr}_{{4}}\hbox {Ru}_{{3}}\hbox {O}_{{10}}$$ Sr 4 Ru 3 O 10 are similar to those of the other three members of the Ruddlesden Popper structured ruthenates, the possible universality of strong coupling of electrons to oxygen-related phonons in $$\hbox {Sr}_{n+1}\hbox {Ru}_{{n}}\hbox {O}_{3n+1}$$ Sr n + 1 Ru n O 3 n + 1 compounds is proposed.

An elevated nitrogen concentration in water is one of the main problems affecting water quality in Mediterranean rivers. The objectives of this study were (1) to evaluate the contribution of the Tafna catchment to the nitrate load entering the Mediterranean Sea, (2) to quantify the impact of agriculture on the nitrate concentration in water bodies, (3) to evaluate nitrate loads entering groundwater, and (4) to quantify the role of reservoirs in nitrate retention. A SWAT model was applied during the period 2003 to 2011. The discharge calibration was based on a previous study by Zettam et al. (2017). NSE efficiencies ranged from 0.421 to 0.75,R(2)ranged from 0.25 to 0.84, and PBIAS ranged from 3.68 to 39.42. The simulations of monthly nitrate loads were satisfactory in the upstream sampling stations, with NSE between 0.48 and 0.65 andR(2)between 0.63 and 0.68. The PBIAS was satisfactory in all the sampling stations (- 36.30 to 10.42). In the downstream sampling stations, the calibration of the monthly nitrate loads was unsatisfactory (NSE ranged from - 0.26 to 0.21 andR(2)ranged from 0.02 to 0.25). Fertilisation was the main N input in the catchment, while the main N output was plant uptake. The Tafna River carried an annual average of 37 to 85.5 t N year(-1)into the Mediterranean Sea. The simulation also showed that reservoirs in the Tafna basin contain a large quantity of nitrates, i.e. 62% on average of the total amount of nitrates transported annually by the Tafna River.

The aim of this study is to examine the trophic state of three reservoirs located in the northwest of Algeria based on the physicochemistry of water and the community of rotifers. The measurements of the physicochemical variables were carried out monthly over a 2-year period from December 2015 to November 2017. The rotifers were sampled simultaneously. Abiotic and biotic indices such as the Carlson index, QB/T, and TSIROT were determined in order to classify the three reservoirs according to their trophic state. Thus, the diversity indices of Shannon-Wiener (H′), Margalef richness index (D), Pielou evenness (J′), and the density were calculated in order to study the structure of the rotifers. The Kruskal-Wallis test confirmed the heterogeneity of the physicochemical quality (P value

The atomic structure and electronic properties of monolayer graphene on a curved multi-nano-vicinal Pt (1 1 1) substrate are investigated with a low-energy electron diffraction, scanning tunneling microscopy and angle-resolved photoemission spectroscopy. Despite graphene grows continuously over the terraces and step bunching areas, the spatial periodicity also varies by varying the vicinal angle of the substrate. This superperiodicity has been evidenced by splitting of first order Pt spots in LEED and from STM. The photoemission spectroscopy unravels that the linearly dispersing π band of graphene is affected by the step periodicity as evidenced by the opening of bandgaps. The gaps opening occurs at the intersection of the main graphene band with Umklapp bands due to the superperiodicity of the one-dimensional nanostructured substrate. The energy and momentum locations of the minigaps change with the superperiodicity, which is related to the spatial periodicity and vicinal angle of the substrate. Our results show a simple way to tune the electronic properties of epitaxial graphene by tuning the substrate vicinality.

The electronic structure of a Bi 0.91 Sb 0.09 single crystal was elucidated at a bisectrix ( 11 2 ¯ ) surface by angle-resolved photoemission spectroscopy using microbeam synchrotron radiation. A Dirac-cone-like dispersion of the surface state was observed at the Γ ¯ point. The detected surface-state band likely corresponds to the one observed in previous quantum transport research (Taskin and Ando, 2009) [14].

Against the backdrop of recent climate change issues, the intensity of dry periods is increasing in semi-arid environments due to high temperatures, evaporation and a shortage of precipitation in summer. The Tafna catchment, which is located in north-western Algeria and is characterised by a Mediterranean climate with a sub-dry tendency, has been subject to severe and prolonged dry periods. In order to understand the impact of prolonged dry periods on biogeochemical processes and nutrient exchange between surface water (SW) and hyporheic water (HW) within the (study) catchment, four sets of samples were taken upstream of the Tafna wadi during low-water (LW) periods over two years (2014–2015). Nitrate, nitrite, ammonium and chloride were measured in surface water (SW) and hyporheic water (HW) at depths of 30, 60 and 100 cm. The results showed a significant loss of nitrate and a considerable increase in ammonium in the hyporheic zone (HZ) during these severe conditions. This could be related to (i) high rates of denitrification and (ii) the process of dissimilatory nitrate reduction to ammonium (DNRA). This study indicated that a severe drought directly affects the nitrogen cycle that occurs in a hyporheic zone (HZ), and thus affects the functioning of this area relative to the wadi system as a whole.

Determining the scattering potential landscape for two-dimensional superlattices provides key insight into fundamental quantum electron phenomena. Theoretical and semiempirical methods have been extensively used to simulate confinement effects of the two-dimensional electron gas (2DEG) on superlattices with a single scatterer in the form of vicinal surfaces and dislocation networks or isolated structures such as quantum corrals and vacancy islands. However, the complexity of the problem increases when the building blocks (or scatterers) are heterogeneous, as in metal-organic nanoporous networks (MONNs), since additional potentials may come into play. Therefore, the parametrization of the surface potential landscape is often inaccurate, leading to incorrect scattering potentials. Here, we address this issue with a combination of scanning tunneling microscopy/spectroscopy, angle resolved photoemission spectroscopy and Kelvin probe force microscopy measurements together with electron plane-wave expansion simulations on a MONN grown on Cu(111). This experimental-Theory approach, enables us to capture the 2DEG response to the intricate scattering potential landscape, and reveals systematic modeling procedures. Starting from a realistic geometry of the system, we determine the repulsive scattering potentials for both molecules and coordinated metal adatoms, the latter contradicting the established simulation framework. Moreover, we reveal local asymmetries and subtle renormalization effects of the 2DEG that relate to the interaction of the MONN and the underlying substrate., We acknowledge the financial support from the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, Grant No. MAT2016-78293-C6), from the Basque Government (Grant No. IT-1255-19), from the regional Government of Aragon (RASMIA project). Part of this work has been performed at the SOLEIL synchrotron at the CASSIOPEE beamline under proposal 20080787. We acknowledge support by the Deutsche Forschungsgemeinschaft (SFB 1249, TP A2 to LHG). SK acknowledges support by Japan Society for the Promotion of Science (JSPS)KAKENHI Grant Number 15K21765. We also acknowledge funding by the Paul Scherrer Institute, the Physics Department of the University of Basel and the Swiss Nanoscience Institute, the Swiss National Science Foundation (Grants # 200020_162512, 206021_144991, 206021_121461) and the Swiss Commission for Technology and Innovation (CTI, 16 465.1 PFNM-NM).

International audience; The behaviour and sources of rare earth elements (REE) in river sediments were investigated at ten stations and two dams of the Tafna basin (Northern Algeria) during contrasting hydrological conditions and using a combination of normalisation procedures, REE anomalies, various REE ratios, and multivariate statistical analysis. The ranking and REE concentrations were in the range of other carbonated areas. The classical fractionation of the heavy REE(HREE) erosion pattern, evidenced from upstream to downstream by the La/Yb or Sm/Yb ratios, was disturbed by the presence of dams, which retained the light REE (LREE) in particular. The hydrological conditions, particle size, and geochemical characteristics controlled the REE patterns. The LREE were associated with clay minerals and HREE with coarse silts, whereas carbonate and particulate organic carbon (POC) did not influence the transport downstream. The total concentration of REE in sediments was not strongly affected by anthropogenic inputs from various sources (industrial activities, and domestic or medical wastes). Indeed, some LREE enrichment and anomalies were detected at a few stations and locally for Gd, Tb, and Yb. However, the anthropogenic contribution can partially be hidden by dilution due to particle erosion. High flow increased the LREE and MREE enrichment and LREE/HREE fractionation in some places due to erosion processes and an-thropic influences (dam releases and local wastes inputs). Middle REE (MREE) and HREE were the most ex-tractable elements unlike LREE (which are the most concentrated), particularly during high water conditions. Finally, the REE demonstrated the impact of natural processes (hydrological, geochemical, and physical) and some anthropogenic disturbances (waste inputs, fertilisers, and dams). This might inspire to develop such investigations in other similar semi-arid basins undergoing various pressures. The use of local bedrock as a reference and a set of geochemical and statistical tools, is recommended.

International audience; One of the most important challenges in the study of topological insulators is the realization of materials that are really insulating in the bulk, in order to emphasize quantum transport in the protected surface states. Irradiation with electron beams is a very promising approach toward this goal. By studying a series of samples of the prototype 3D topological insulator Bi 2 Te 3 , we show that while the topological properties of Dirac surface states are preserved after electron irradiation, their relaxation dynamics are very sensitive to the related modifications of the bulk properties. Using time-and angle-resolved photoelectron spectroscopy, we can reveal two distinct relaxation regimes after optical excitation for non-irradiated and irradiated samples. While the faster regime, corresponding to the first few picoseconds, presents a similar temporal evolution of the photoexcited population for all studied samples, the slower regime is strongly influenced by the controlled generation of defects in the bulk lattice. By adjusting the irradiation parameters in this class of materials, one can thus not only change the bulk transport properties but also tune the ultrafast response of the topological surface states.

The dataset (Data File S1; DOI: 10.6084/m9.figshare.8863721) and the R code used to generate the results (Code S1; DOI: 10.6084/m9.figshare.8863655), including step by step explanations of the statistical tests, have been deposited in Figshare Digital Repository (https://figshare.com/projects/Sediment_Respiration_Pulses_in_Intermittent_Rivers_and_Ephemeral_Streams/66104)., Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO2) emissions is largely undetermined. In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of CO2. We present a global study examining sediments from 200 dry IRES reaches spanning multiple biomes. Results from standardized assays show that mean respiration increased 32–66-fold upon sediment rewetting. Structural equation modelling indicates that this response was driven by sediment texture and organic matter quantity and quality, which, in turn, were influenced by climate, land use and riparian plant cover. Our estimates suggest that respiration pulses resulting from rewetting of IRES sediments could contribute significantly to annual CO2 emissions from the global stream network, with a single respiration pulse potentially increasing emission by 0.2–0.7%. As the spatial and temporal extent of IRES increases globally, our results highlight the importance of recognizing the influence of wetting-drying cycles on respiration and CO2 emissions in stream networks., We thank Y. Etxeberria, L. Sánchez, C. Gutiérrez, G. LeGoff and B. Launay for laboratory support. DvS was supported by a Short-Term Scientific Mission of the COST Action CA15113 (SMIRES, Science and Management of Intermittent Rivers and Ephemeral Streams, www.smires.eu), supported by COST (European Cooperation in Science and Technology) and received additional funding from the EU’s 7th Framework Programme for research, technological development and demonstration under grant agreement No. 603629 (GLOBAQUA) and a Grant for Research Groups of the Basque University System (IT-951-16) funded by the Basque Government. RM and BO were supported by the Spanish Ministry of Science, Innovation and Universities through project C-HYDROCHANGE (CGL2017-86788-C3-2-P and CGL2017-86788-C3-3-P). FA was funded by the Swiss National Science Foundation grants No. PP00P3_150698 and PP00P3_179089. NC was supported by the EU project LIFE+ TRivers (LIFE13 ENV/ES/000341). SDL received funding from the EU’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 748625. PP and MP were supported by INTER-COST project LTC17017. The authors declare that they have no competing interests.

This study investigated the biodiversity and hydrochemistry of seven unconfined aquifers located in two hydrogeological complexes in the north-western region of Algeria. The aim of the study was to: (1) contribute new data on the biodiversity and distribution patterns of groundwater fauna in groundwater bodies in North Africa, (2) assess whether the current biodiversity patterns of groundwater taxa reflect the difference in aquifer type, hydrogeological conditions and hydrochemistry, and (3) evaluate the role of hydrogeological, geographical and physicochemical variables in determining the distribution pattern of groundwater invertebrates. Sixty-three wells were investigated between August 2010 and June 2013. In total, 41,297 specimens belonging to 51 taxa, 10 of which were crustaceans, were collected during the survey. Taxa abundances varied significantly between aquifer types, but not between the two hydrogeological complexes (continental and littoral). The groundwater assemblages collected in seven aquifers in northwest Algeria differed significantly between aquifer types in this region. The distribution of groundwater fauna across the whole study area was primarily affected by distance to streams, the geological period and electrical conductivity. Overall, the assemblages showed a spatial distribution that to some extent mirrored the hydrogeological and hydrochemical conditions of groundwater in the north-western part of Algeria. These findings suggest that groundwater biota, and crustaceans in particular, may play a key role in distinguishing between the typologies of the investigated aquifers. This study contributes to knowledge of current groundwater biodiversity in northwest Algeria and demonstrates that this knowledge is still far from being complete.

Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56%–98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events., In this study we experimentally simulated under laboratory conditions rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase from intermittent rivers and ephemeral streams covering global spatial scale. We determined the amounts and quality of the leached nutrients and dissolved organic matter, assessed their inter‐substrate and cross‐climate differences, and estimated areal fluxes from 1 m2 of riverbeds. In addition, we evaluated the variance in leachate characteristics related to selected environmental variables and substrate characteristics.

International audience

Producing a usable semiconducting form of graphene has plagued the development of graphene electronics for nearly two decades. Now that new preparation methods have become available, graphene's intrinsic properties can be measured and the search for semiconducting graphene has begun to produce results. This is the case of the first graphene "buffer" layer grown on SiC(0001) presented in this work. We show, contrary to assumptions of the last forty years, that the buffer graphene layer is not commensurate with SiC. The new modulated structure we've found resolves a long standing contradiction where ab initio calculations expect a metallic buffer, while experimentally it is found to be a semiconductor. Model calculations using the new incommensurate structure show that the semiconducting $\pi$-band character of the buffer comes from partially hybridized graphene incommensurate boundaries surrounding unperturbed graphene islands., Comment: 17 pages, 4 figures, 1 table, 47 references, supplemental material: 15 pages, 4 figures

The Kondo ground state can arise in surface-supported organometallic systems, such as the 3d transition metal phthalocyanines, as a result of the hybridization of the 3d localized orbitals with the underlying metal substrate electrons. Low-temperature scanning tunneling spectroscopy can identify the Kondo states as a zero-bias anomaly in the differential conductance curves, often localized in close proximity with the 3d metal center. However, the information on the symmetry of the Kondo state, on the exact shape of the spectral function, and on the magnetic state is generally missing from the experimental data. We apply complementary techniques, i.e., scanning tunneling spectroscopy, resonant photoemission spectroscopy, and X-ray magnetic circular dichroism, to identify the Kondo state, the orbital symmetry, and the magnetic moment of Fe-Phthalocyanine chains formed by two structural phases with increasing molecular density: first ×5 and at higher coverage ×7 FePc ordered chain structures assembled on the Au(110) surface. The experimental data suggest the presence of a Kondo state only in the ×5 phase, at lower molecular density, with a Kondo temperature of about 60 K, having parent states with the dxz, dyz symmetry, that cancels the magnetic moment of the molecules at low temperatures.

A synergistic effect between strong electron correlation and spin-orbit interaction (SOI) has been theoretically predicted to result in a new topological state of quantum matter on Kondo insulators (KIs), so-called topological Kondo insulators (TKIs). One TKI candidate has been experimentally observed on the KI SmB6(001), and the origin of the surface states (SS) and the topological order of SmB6 has been actively discussed. Here, we show a metallic SS on the clean surface of another TKI candidate YbB12(001), using angle-resolved photoelectron spectroscopy. The SS showed temperature-dependent reconstruction corresponding with the Kondo effect observed for bulk states. Despite the low-temperature insulating bulk, the reconstructed SS with c-f hybridization was metallic, forming a closed Fermi contour surrounding $\bar{\Gamma}$ on the surface Brillouin zone and agreeing with the theoretically expected behavior for SS on TKIs. These results demonstrate the temperature-dependent holistic reconstruction of two-dimensional states localized on KIs surface driven by the Kondo effect., Comment: 15 pages, 4 figures

A high spin polarization of states around the Fermi level, EF, at room temperature has been measured in the past at the interface between a few molecular candidates and the ferromagnetic metal Co. Is this promising property for spintronics limited to these candidates? Previous reports suggested that certain conditions, such as strong ferromagnetism, i.e., a fully occupied spin-up d band of the ferromagnet, or the presence of π bonds on the molecule, i.e., molecular conjugation, needed to be met. What rules govern the presence of this property? We have performed spin-resolved photoemission spectroscopy measurements on a variety of such interfaces. We find that this property is robust against changes to the molecule and ferromagnetic metal's electronic properties, including the aforementioned conditions. This affirms the generality of highly spin-polarized states at the interface between a ferromagnetic metal and a molecule and augurs bright prospects toward integrating these interfaces within organic spintronic devices.

Detailed surface electronic structure on the Bi/InSb(001) surface hosting Tomonaga–Luttinger liquid was observed by angle-resolved photoelectron spectroscopy (ARPES) with synchrotron radiation. ARPES energy distribution curves (EDCs) around the Fermi level indicated the two separate features dispersing with different Fermi velocity but approaching each other. Two possible scenarios, elemental excitations from separate spin/charge terms and those from independent two surface bands, are discussed based on the experimental results.

International audience; We investigate black phosphorus by time- and angle-resolved photoelectron spectroscopy. The electrons excited by 1.57 eV photons relax down to a conduction band minimum within 1 ps. Despite the low band gap value, no relevant amount of carrier multiplication could be detected at an excitation density 3–6 × 1019 cm–3. In the thermalized state, the band gap renormalization is negligible up to a photoexcitation density that fills the conduction band by 150 meV. Astonishingly, a Stark broadening of the valence band takes place at an early delay time. We argue that electrons and holes with a high excess energy lead to inhomogeneous screening of near surface fields. As a consequence, the chemical potential is no longer pinned in a narrow impurity band.

Gray tin, also known as $\ensuremath{\alpha}$-Sn, can be turned into a three-dimensional topological insulator (3D-TI) by strain and finite-size effects. Such room-temperature 3D-TI is peculiarly interesting for spintronics due to the spin-momentum locking along the Dirac cone (linear dispersion) of the surface states. Angle-resolved photoemission spectroscopy (ARPES) has been used to investigate the dispersion close to the Fermi level in thin (001)-oriented epitaxially strained films of $\ensuremath{\alpha}$-Sn for different film thicknesses as well as for different capping layers (Al, ${\mathrm{AlO}}_{x}$, and MgO). Indeed a proper capping layer is necessary to be able to use $\ensuremath{\alpha}$-Sn surface states for spintronic applications. In contrast with free surfaces or surfaces coated with Ag, coating the $\ensuremath{\alpha}$-Sn surface with Al or ${\mathrm{AlO}}_{x}$ leads to a drop in the Fermi level below the Dirac point, and an important consequence for electronic transport is the presence of bulk states at the Fermi level. $\ensuremath{\alpha}$-Sn films coated by ${\mathrm{AlO}}_{x}$ are studied by electrical magnetotransport: Despite magnetotransport properties of the bulk electronic states of the ${\mathrm{\ensuremath{\Gamma}}}_{8}$ band playing an important role as suggested by ab initio calculations, there is clear evidence of surface states revealed by Shubnikov--de Haas oscillations corresponding to the ARPES observation.

Author(s): Kuo, CT; Lin, SC; Conti, G; Pi, ST; Moreschini, L; Bostwick, A; Meyer-Ilse, J; Gullikson, E; Kortright, JB; Nemsak, S; Rault, JE; Le Fevre, P; Bertran, F; Santander-Syro, AF; Vartanyants, IA; Pickett, WE; Saint-Martin, R; Taleb-Ibrahimi, A; Fadley, CS | Abstract: A major remaining challenge in the superconducting cuprates is the unambiguous differentiation of the composition and electronic structure of the CuO2 layers and those of the intermediate layers. The large c axis for these materials permits employing soft x-ray (930.3 eV) standing wave (SW) excitation in photoemission that yields atomic layer-by-layer depth resolution of these properties. Applying SW photoemission to Bi2Sr2CaCu2O8+δ yields the depth distribution of atomic composition and the layer-resolved densities of states. We detect significant Ca presence in the SrO layers and oxygen bonding to three different cations. The layer-resolved valence electronic structure is found to be strongly influenced by the atomic supermodulation structure, as determined by comparison to density functional theory calculations, by Ca-Sr intermixing, and by correlation effects associated with the Cu 3d-3d Coulomb interaction, further clarifying the complex interactions in this prototypical cuprate. Measurements of this type for other quasi-two-dimensional materials with large c represent a promising future direction.

Very few studies have evaluated the role of the hyporheic zone (HZ) in aquatic ecosystem functioning or the factors driving hyporheic exchange flows on a large scale, especially in a semi-arid environment such as the Tafna watershed in Algeria. To understand this role through time and space, hydrogeochemical parameters, particularly nitrate concentrations (NO3–N), were measured monthly between February 2013 and April 2014 in surface water (SW), interstitial water (IW) and groundwater (GW) along a 170-km stretch from the river’s source to the outlet into the main stream of the Tafna River and its Isser and Chouly tributaries. The significant longitudinal evolution of NO3–N in the HZ was related to stream order and distance from the source. Moreover, the study indicated a significant difference between nitrate concentrations in the riffles (R) and pools (P) of the Tafna wadi. Principal component analysis (PCA) revealed the considerable impact of agriculture on nitrate concentrations. This study indicated on a large scale that nitrate-rich HZ contributed to increasing surface nitrate concentrations in upwelling sites and could be an important nitrate source for downstream SW, particularly during low-water (LW) periods when the Tafna can run dry on the surface. Thus, these results underline the importance of hyporheic zones functioning to the water quality of the watershed (process of enrichment and retention of nitrogen).