Search

Sr2IrO4 has often been described via a simple, one-band pseudospin-12 model subject to electron-electron interactions on a square lattice, fostering analogies with cuprate superconductors believed to be well described by a similar model. In this work we argue - based on a detailed study of the low-energy electronic structure by circularly polarized spin and angle-resolved photoemission spectroscopy combined with dynamical mean-field theory calculations - that a pseudospin-12 model fails to capture the full complexity of the system. We show instead that a realistic multiband Hubbard Hamiltonian, accounting for the full correlated t2g manifold, provides a detailed description of the interplay between spin-orbital entanglement and electron-electron interactions and yields quantitative agreement with experiments. Our analysis establishes that the j3/2 states make up a substantial percentage of the low-energy spectral weight, i.e., approximately 74% as determined from the integration of the j-resolved spectral function in the 0 to -1.64eV energy range. The results in our work are of relevance not only to Ir-based materials but also more generally to multiorbital materials with closely spaced energy scales.

AgCrS e 2 exhibits remarkably high ionic conduction, an inversion symmetry-breaking structural transition, and is host to complex non-colinear magnetic orders. Despite its attractive physical and chemical properties and its potential for technological applications, studies of this compound to date are focused almost exclusively on bulk samples. Here, we report the growth of AgCrS e 2 thin films via molecular beam epitaxy. Single-orientated epitaxial growth was confirmed by x-ray diffraction, while resonant photoemission spectroscopy measurements indicate a consistent electronic structure as compared to bulk single crystals. We further demonstrate significant flexibility of the grain morphology and cation stoichiometry of this compound via control of the growth parameters, paving the way for the targeted engineering of the electronic and chemical properties of AgCrS e 2 in thin-film form. [ABSTRACT FROM AUTHOR]

We report on epitaxial growth of Bi2Se3 topological insulator thin films by Pulsed Laser Deposition (PLD). X-ray diffraction investigation confirms that Bi2Se3 with a single (001)-orientation can be obtained on several substrates in a narrow (i.e., 20 °C) range of deposition temperatures and at high deposition pressure (i.e., 0.1 mbar). However, only films grown on (001)-Al2O3 substrates show an almost-unique in-plane orientation. In-situ spin-resolved angular resolved photoemission spectroscopy experiments, performed at the NFFA-APE facility of IOM-CNR and Elettra (Trieste), show a single Dirac cone with the Dirac point at EB ~ 0:38 eV located in the center of the Brillouin zone and the spin polarization of the topological surface states. These results demonstrate that the topological surface state can be obtained in PLD-grown Bi2Se3 thin films. [ABSTRACT FROM AUTHOR]

The electronic properties of hole- and electron-doped manganites were probed by a combination of x-ray absorption and photoemission spectroscopies. Hole-doped La 0.7 Ba 0.3 MnO 3 and electron-doped La 0.7 Ce 0.3 MnO 3 thin films were epitaxially grown on SrTiO 3 substrates by means of pulsed laser deposition. Ex-situ x-ray diffraction demonstrated the substrate/film epitaxy relation and in-situ low energy electron diffraction provided evidence of high structural order of film surfaces. By combining synchrotron x-ray absorption and x-ray photoemission spectroscopy, evidence of Mn ions into a 2+ state as a result of the Ce 4 + substitution in the electron-doped manganites was provided. Angular resolved photo-emission spectroscopy (ARPES) results showed a predominance of z2-orbitals at the surface of both hole- and, unexpectedly, electron-doped manganites thus questioning the validity of the commonly accepted scenario describing the electron filling in manganites' 3d orbitals in oxide manganites. The precise determination of the electronic and orbital properties of the terminating layers of oxide manganites paves the way for engineering multi-layered heterostructures thus leading to novel opportunities in the field of quantum electronics. • The orbital character of surface electronic states of oxide manganites was identified • Epitaxial hole- (electron) doped La 0.7 (Ba,Ce) 0.3 MnO 3 thin films were grown by PLD • XAS and XPS on in-situ transferred samples provided evidence of a Ce 4 + in LCeMO • ARPES data always indicated a z2-orbital occupation in both LBMO and LCeMO • Our results are at odds with the common description of electron filling in 3d orbitals. [ABSTRACT FROM AUTHOR]

The transition-metal chalcogenides include some of the most important and ubiquitous families of 2D materials. They host an exceptional variety of electronic and collective states, which can in principle be readily tuned by combining different compounds in van der Waals heterostructures. Achieving this, however, presents a significant materials challenge. The highest quality heterostructures are usually fabricated by stacking layers exfoliated from bulk crystals, which - while producing excellent prototype devices - is time consuming, cannot be easily scaled, and can lead to significant complications for materials stability and contamination. Growth via the ultra-high vacuum deposition technique of molecular-beam epitaxy (MBE) should be a premier route for 2D heterostructure fabrication, but efforts to achieve this are complicated by non-uniform layer coverage, unfavorable growth morphologies, and the presence of significant rotational disorder of the grown epilayer. This work demonstrates a dramatic enhancement in the quality of MBE grown 2D materials by exploiting simultaneous deposition of a sacrificial species from an electron-beam evaporator during the growth. This approach dramatically enhances the nucleation of the desired epi-layer, in turn enabling the synthesis of large-area, uniform monolayers with enhanced quasiparticle lifetimes, and facilitating the growth of epitaxial van der Waals heterostructures., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Metallic ferromagnetic transition metal dichalcogenides have emerged as important building blocks for scalable magnetic and memory applications. Downscaling such systems to the ultrathin limit is critical to integrate them into technology. Here, we achieved layer-by-layer control over the transition metal dichalcogenide Cr 1.6 Te 2 by using pulsed laser deposition, and we uncovered the minimum critical thickness above which room-temperature magnetic order is maintained. The electronic and magnetic structures are explored experimentally and theoretically, and it is shown that the films exhibit strong in-plane magnetic anisotropy as a consequence of large spin-orbit effects. Our study elucidates both magnetic and electronic properties of Cr 1.6 Te 2 and corroborates the importance of intercalation to tune the magnetic properties of nanoscale materials' architectures.

The relation between crystal symmetries, electron correlations and electronic structure steers the formation of a large array of unconventional phases of matter, including magneto-electric loop currents and chiral magnetism 1-6 . The detection of such hidden orders is an important goal in condensed-matter physics. However, until now, non-standard forms of magnetism with chiral electronic ordering have been difficult to detect experimentally 7 . Here we develop a theory for symmetry-broken chiral ground states and propose a methodology based on circularly polarized, spin-selective, angular-resolved photoelectron spectroscopy to study them. We use the archetypal quantum material Sr 2 RuO 4 and reveal spectroscopic signatures that, despite being subtle, can be reconciled with the formation of spin-orbital chiral currents at the surface of the material 8-10 . As we shed light on these chiral regimes, our findings pave the way for a deeper understanding of ordering phenomena and unconventional magnetism., (© 2024. The Author(s).)

Closing the band gap of a semiconductor into a semimetallic state gives a powerful potential route to tune the electronic energy gains that drive collective phases like charge density waves (CDWs) and excitonic insulator states. We explore this approach for the controversial CDW material monolayer (ML) TiSe 2 by engineering its narrow band gap to the semimetallic limit of ML-TiTe 2 . Using molecular beam epitaxy, we demonstrate the growth of ML-TiTe 2 x Se 2(1- x ) alloys across the entire compositional range and unveil how the (2 × 2) CDW instability evolves through the normal state semiconductor-semimetal transition via in situ angle-resolved photoemission spectroscopy. Through model electronic structure calculations, we identify how this tunes the relative strength of excitonic and Peierls-like coupling, demonstrating band gap engineering as a powerful method for controlling the microscopic mechanisms underpinning the formation of collective states in two-dimensional materials.

Engineering surfaces and interfaces of materials promises great potential in the field of heterostructures and quantum matter designers, with the opportunity to drive new many-body phases that are absent in the bulk compounds. Here, we focus on the magnetic Weyl kagome system Co 3 Sn 2 S 2 and show how for the terminations of different samples the Weyl points connect differently, still preserving the bulk-boundary correspondence. Scanning tunneling microscopy has suggested such a scenario indirectly, and here, we probe the Fermiology of Co 3 Sn 2 S 2 directly, by linking it to its real space surface distribution. By combining micro-ARPES and first-principles calculations, we measure the energy-momentum spectra and the Fermi surfaces of Co 3 Sn 2 S 2 for different surface terminations and show the existence of topological features depending on the top-layer electronic environment. Our work helps to define a route for controlling bulk-derived topological properties by means of surface electrostatic potentials, offering a methodology for using Weyl kagome metals in responsive magnetic spintronics.

Two-dimensional van der Waals magnetic semiconductors display emergent chemical and physical properties and hold promise for novel optical, electronic and magnetic "few-layers" functionalities. Transition-metal iodides such as CrI 3 and VI 3 are relevant for future electronic and spintronic applications; however, detailed experimental information on their ground state electronic properties is lacking often due to their challenging chemical environment. By combining X-ray electron spectroscopies and first-principles calculations, we report a complete determination of CrI 3 and VI 3 electronic ground states. We show that the transition metal-induced orbital filling drives the stabilization of distinct electronic phases: a wide bandgap in CrI 3 and a Mott insulating state in VI 3 . Comparison of surface-sensitive (angular-resolved photoemission spectroscopy) and bulk-sensitive (X-ray absorption spectroscopy) measurements in VI 3 reveals a surface-only V 2+ oxidation state, suggesting that ground state electronic properties are strongly influenced by dimensionality effects. Our results have direct implications in band engineering and layer-dependent properties of two-dimensional systems.

Background: The aim of this study was to analyze the Adverse Events Reporting System (AERS) Database of the Food and Drug Administration (FDA), investigating the characteristics of pediatric adverse drug reactions (ADRs) and describing the effective participation of healthcare professionals in the reporting activity., Methods: Reports of ADRs were obtained from the FDA website. Only ADRs in pediatric subjects (divided by age, by country and by professional category) were included into the analysis. The drugs suspected as primary cause of the ADRs in pediatric subjects and their principal anatomic group according to the Anatomical Therapeutic Chemical Classification system were considered. To classify the ADRs, the Medical Dictionary for Regularity Activities terminology was adopted., Results: Between 2008 and 2012, FDA collected 113,077 ADRs in pediatric patients. Of the total pediatric ADR reports, those performed by medical doctors were 32%, followed by consumers (26%) and healthcare professionals (25%). Most of the ADR reports were related to the adolescent group (39%). Healthcare professionals resulted the category with the highest rate of ADR reports in neonates and infants. Drugs acting on nervous system and antineoplastic/immunomodulating agents were the most involved the pediatric ADR reports. Pyrexia, convulsion, vomiting and accidental overdose were the reactions more reported both from healthcare professionals and medical doctors., Conclusions: The present study describes the pediatric ADR reports of the FDA database through healthcare professional's perspective, describing the various aspects of pediatric pharmacovigilance.

The formation and the evolution of electronic metallic states localized at the surface, commonly termed 2D electron gas (2DEG), represents a peculiar phenomenon occurring at the surface and interface of many transition metal oxides (TMO). Among TMO, titanium dioxide (TiO 2 ), particularly in its anatase polymorph, stands as a prototypical system for the development of novel applications related to renewable energy, devices and sensors, where understanding the carrier dynamics is of utmost importance. In this study, angle-resolved photo-electron spectroscopy (ARPES) and X-ray absorption spectroscopy (XAS) are used, supported by density functional theory (DFT), to follow the formation and the evolution of the 2DEG in TiO 2 thin films. Unlike other TMO systems, it is revealed that, once the anatase fingerprint is present, the 2DEG in TiO 2 is robust and stable down to a single-unit-cell, and that the electron filling of the 2DEG increases with thickness and eventually saturates. These results prove that no critical thickness triggers the occurrence of the 2DEG in anatase TiO 2 and give insight in formation mechanism of electronic states at the surface of TMO., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

We unravel the interplay of topological properties and the layered (anti)ferromagnetic ordering in EuSn 2 P 2 , using spin and chemical selective electron and X-ray spectroscopies supported by first-principle calculations. We reveal the presence of in-plane long-range ferromagnetic order triggering topological invariants and resulting in the multiple protection of topological Dirac states. We provide clear evidence that layer-dependent spin-momentum locking coexists with ferromagnetism in this material, a cohabitation that promotes EuSn 2 P 2 as a prime candidate axion insulator for topological antiferromagnetic spintronics applications., Competing Interests: The authors declare no competing interest., (Copyright © 2022 the Author(s). Published by PNAS.)

Topological insulators are materials with time-reversal symmetric states of matter in which an insulating bulk is surrounded by protected Dirac-like edge or surface states. Among topological insulators, Bi2Se3 has attracted special attention due to its simple surface band structure and its relatively large band gap that should enhance the contribution of its surface to transport, which is usually masked by the appearance of defects. In order to avoid this difficulty, several features characteristic of topological insulators in the quantum regime, such as the weak-antilocalization effect, can be explored through magnetotransport experiments carried out on thin films of this material. Here, we review the existing literature on the magnetotransport properties of Bi2Se3 thin films, paying thorough attention to the weak-antilocalization effect, which is omnipresent no matter the film quality. We carefully follow the different situations found in reported experiments, from the most ideal situations, with a strong surface contribution, towards more realistic cases where the bulk contribution dominates. We have compared the transport data found in literature to shed light on the intrinsic properties of Bi2Se3, finding a clear relationship between the mobility and the phase coherence length of the films that could trigger further experiments on transport in topological systems.

Purpose: The reporting of suspected adverse drug reactions (ADRs) is starting to become routine to nurses. The aim of this review is to underline the role of clinical and community health nurses in pharmacovigilance and to promote their effective participation in ADR reporting in different countries and for patients of different ages., Methods: The PubMed, Scopus and ISI Web of Science databases were searched for research articles published between January 1985 and April 2017 using the search items "pharmacovigilance" AND "nurse;" "adverse drug reaction report" AND "nurse;" "community health nurse" AND "adverse drug reaction.", Results: A total of 987 articles were identified using our search strategy, of which 180 articles remained over after the removal of duplicate articles. Of these 180 studies, upon full review we identified 24 which met the inclusion/exclusion criteria and included these in our review. ADR reports by clinical nurses in some countries are comparable in quality and number to those submitted by physicians or pharmacists. Data on ADRs reported by community nurses are currently not available. However, numerous publications emphasized the challenges faced by nurses in reporting ADRs and the need to include pharmacovigilance training in both clinical and community health nurse academic education., Conclusions: Nurses are central actors in pharmacovigilance activities, particularly in identifying ADRs which remain outside the reach of other healthcare providers and in being fundamental to the preservation of the health of patients and of the entire community, with attention to the more vulnerable patients, such as children and the elderly.

We report the study of anatase TiO 2 (001)-oriented thin films grown by pulsed laser deposition on LaAlO 3 (001). A combination of in situ and ex situ methods has been used to address both the origin of the Ti 3+ -localized states and their relationship with the structural and electronic properties on the surface and the subsurface. Localized in-gap states are analyzed using resonant X-ray photoelectron spectroscopy and are related to the Ti 3+ electronic configuration, homogeneously distributed over the entire film thickness. We find that an increase in the oxygen pressure corresponds to an increase in Ti 3+ only in a well-defined range of deposition pressure; outside this range, Ti 3+ and the strength of the in-gap states are reduced.

Complete photoemission experiments, enabling measurement of the full quantum set of the photoelectron final state, are in high demand for studying materials and nanostructures whose properties are determined by strong electron and spin correlations. Here the implementation of the new spin polarimeter VESPA (Very Efficient Spin Polarization Analysis) at the APE-NFFA beamline at Elettra is reported, which is based on the exchange coupling between the photoelectron spin and a ferromagnetic surface in a reflectometry setup. The system was designed to be integrated with a dedicated Scienta-Omicron DA30 electron energy analyzer allowing for two simultaneous reflectometry measurements, along perpendicular axes, that, after magnetization switching of the two targets, allow the three-dimensional vectorial reconstruction of the spin polarization to be performed while operating the DA30 in high-resolution mode. VESPA represents the very first installation for spin-resolved ARPES (SPARPES) at the Elettra synchrotron in Trieste, and is being heavily exploited by SPARPES users since autumn 2015.