How the interacting electronic states and phases of layered transition-metal dichalcogenides evolve when thinned to the single-layer limit is a key open question in the study of two-dimensional ...materials. Here, we use angle-resolved photoemission to investigate the electronic structure of monolayer VSe2 grown on bilayer graphene/SiC. While the global electronic structure is similar to that of bulk VSe2, we show that, for the monolayer, pronounced energy gaps develop over the entire Fermi surface with decreasing temperature below T c = 140 ± 5 K, concomitant with the emergence of charge-order superstructures evident in low-energy electron diffraction. These observations point to a charge-density wave instability in the monolayer that is strongly enhanced over that of the bulk. Moreover, our measurements of both the electronic structure and of X-ray magnetic circular dichroism reveal no signatures of a ferromagnetic ordering, in contrast to the results of a recent experimental study as well as expectations from density functional theory. Our study thus points to a delicate balance that can be realized between competing interacting states and phases in monolayer transition-metal dichalcogenides.
Abstract
Pressure represents a clean tuning parameter for traversing the complex phase diagrams of interacting electron systems, and as such has proved of key importance in the study of quantum ...materials. Application of controlled uniaxial pressure has recently been shown to more than double the transition temperature of the unconventional superconductor Sr
2
RuO
4
, leading to a pronounced peak in
T
c
versus strain whose origin is still under active debate. Here we develop a simple and compact method to passively apply large uniaxial pressures in restricted sample environments, and utilise this to study the evolution of the electronic structure of Sr
2
RuO
4
using angle-resolved photoemission. We directly visualise how uniaxial stress drives a Lifshitz transition of the γ-band Fermi surface, pointing to the key role of strain-tuning its associated van Hove singularity to the Fermi level in mediating the peak in
T
c
. Our measurements provide stringent constraints for theoretical models of the strain-tuned electronic structure evolution of Sr
2
RuO
4
. More generally, our experimental approach opens the door to future studies of strain-tuned phase transitions not only using photoemission but also other experimental techniques where large pressure cells or piezoelectric-based devices may be difficult to implement.
Using photoemission spectroscopy techniques, we show that oxygen intercalation is achieved on an extended layer of epitaxial graphene on Ir(111), which results in the “lifting” of the graphene layer ...and in its decoupling from the metal substrate. The oxygen adsorption below graphene proceeds as on clean Ir(111), giving only a slightly higher oxygen coverage. Upon lifting, the C 1s signal shows a downshift in binding energy, due to the charge transfer to graphene from the oxygen-covered metal surface. Moreover, the characteristic spectral signatures of the graphene–substrate interaction in the valence band are removed, and the spectrum of strongly hole-doped, quasi free-standing graphene with a single Dirac cone around the K̅ point is observed. The oxygen can be deintercalated by annealing, and this process takes place at around T = 600 K, in a rather abrupt way. A small amount of carbon atoms is lost, implying that graphene has been etched. After deintercalation graphene restores its interaction with the Ir(111) substrate. Additional intercalation/deintercalation cycles readily occur at lower oxygen doses and temperatures, consistently with an increasingly defective lattice. Our findings demonstrate that oxygen intercalation is an efficient method for fully decoupling an extended layer of graphene from a metal substrate, such as Ir(111). They pave the way for the fundamental research on graphene, where extended, ordered layers of free-standing graphene are important and, due to the stability of the intercalated system in a wide temperature range, also for the advancement of next-generation graphene-based electronics.
There has been widespread interest in using interfaces of transition-metal oxides as a platform to control not only their electronic structure, as in semiconductor heterostructures, but also to tune ...between different collective phases. A major goal is to realize states of the quantum many-body system that are not found in the bulk phase diagrams of the constituent materials. Here, we perform a combined experimental and theoretical study of the delafossite oxide metals PdCoO
2
and PdCrO
2
, finding how electronic reconstructions at their polar surfaces drive instabilities to itinerant surface ferromagnetism. Neither compound supports ferromagnetism in bulk, with PdCrO
2
a bulk antiferromagnet, demonstrating how a delicate competition of magnetic correlations can be engineered by intrinsic self-doping at a polar surface or interface.
The ability to modulate the collective properties of correlated electron systems at their interfaces and surfaces underpins the burgeoning field of “designer” quantum materials. Here, we show how an electronic reconstruction driven by surface polarity mediates a Stoner-like magnetic instability to itinerant ferromagnetism at the Pd-terminated surface of the nonmagnetic delafossite oxide metal PdCoO
2
. Combining angle-resolved photoemission spectroscopy and density-functional theory calculations, we show how this leads to a rich multiband surface electronic structure. We find similar surface state dispersions in PdCrO
2
, suggesting surface ferromagnetism persists in this sister compound despite its bulk antiferromagnetic order.
The interplay between spin–orbit coupling and structural inversion symmetry breaking in solids has generated much interest due to the nontrivial spin and magnetic textures which can result. Such ...studies are typically focused on systems where large atomic number elements lead to strong spin–orbit coupling, in turn rendering electronic correlations weak. In contrast, here we investigate the temperature-dependent electronic structure of Ca3Ru2O7, a 4d oxide metal for which both correlations and spin–orbit coupling are pronounced and in which octahedral tilts and rotations combine to mediate both global and local inversion symmetry-breaking polar distortions. Our angle-resolved photoemission measurements reveal the destruction of a large hole-like Fermi surface upon cooling through a coupled structural and spin-reorientation transition at 48 K, accompanied by a sudden onset of quasiparticle coherence. We demonstrate how these result from band hybridization mediated by a hidden Rashba-type spin–orbit coupling. This is enabled by the bulk structural distortions and unlocked when the spin reorients perpendicular to the local symmetry-breaking potential at the Ru sites. We argue that the electronic energy gain associated with the band hybridization is actually the key driver for the phase transition, reflecting a delicate interplay between spin–orbit coupling and strong electronic correlations and revealing a route to control magnetic ordering in solids.
Historically, pre-clinical and clinical studies in human medicine have provided new insights, pushing forward the contemporary knowledge. The new results represented a motivation for investigators in ...specific fields of veterinary medicine, who addressed the same research topics from different perspectives in studies based on experimental and spontaneous animal disease models. The study of different pheno-genotypic contexts contributes to the confirmation of translational models of pathologic mechanisms. This review provides an overview of EMT and MET processes in both human and canine species. While human medicine rapidly advances, having a large amount of information available, veterinary medicine is not at the same level. This situation should provide motivation for the veterinary medicine research field, to apply the knowledge on humans to research in pets. By merging the knowledge of these two disciplines, better and faster results can be achieved, thus improving human and canine health.
Abstract
The single-band, quasi-two dimensional metals PdCoO
2
and PtCoO
2
have recently come to prominence because of their extremely long mean free paths, which establish them as some of the most ...electronically pure materials known, and as potential hosts of previously unobservable regimes of electronic transport. To fully establish their magnetotransport properties, we have studied the magnetoresistance and Hall effect in bulk single crystals to which electrical contacts have been made with high precision using focused ion beam machining. We observe a strong temperature dependence of the Hall resistivity in small applied fields, linked to a large violation of Kohler’s rule in the magnetoresistance. We discuss the extent to which these observations can be accounted for by standard transport theory.
We unravel the interplay of topological properties and the layered (anti)ferromagnetic ordering in EuSn2P2, 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 EuSn2P2 as a prime candidate axion insulator for topological antiferromagnetic spintronics applications.
Since its introduction as a clinical technique, robotic surgery has been extended to different fields of surgery. However, the indications as well as the number of robotic procedures varied in ...different institutions. The aim of this investigation was to evaluate the current use of robotic surgery in general and digestive surgery in Switzerland.
All Swiss surgical departments that are recognized training institutes for postgraduate training in surgery by the Swiss Institute of Medical Education (SIWF) were queried with a detailed questionnaire regarding the use of robotic surgery techniques and were analyzed regarding hospital size and type of hospital.
Ninety-three departments were queried, and 67 % (n=63) answered the survey. Fifty-eight were public, and five were private institutions. Seventeen (26 %) of the queried departments used robotic surgery in digestive surgery. Four out of 17 (23 %) of the departments that performed robotic surgery were private hospitals, while 13 (77 %) were public institutions. In the majority of departments, robotic surgery of the rectum (n=12; 70.6 %) and colon (n=11; 64.7 %) was performed, followed by hernia procedures (n=8; 47.1 %) and fundoplication (n=7; 41.2 %). Less frequently, pancreatic resections (n=5; 29.4 %), cholecystectomy (n=4; 23.5 %), adrenalectomy (n=4; 23.5 %), gastric bypass (n=3; 17.7 %), gastric sleeve (n=3; 17.7 %), hepatic procedures (n=2; 11.7 %), or small bowel resections (n=1; 5.9 %) were performed as robotic procedures. More than 25 procedures per year per department were performed for hernia surgery (n=5 departments), gastric bypass (n=2 departments), cholecystectomy, fundoplication, and colon surgery (each n=1 department).
The number and range of robotic procedures performed in Switzerland varied widely. Higher accreditation for general surgery or subspecialization of visceral surgery of the department was positively associated with the use of robotic techniques, reflecting an unequal availability of robotic surgery.
We report on the growth and characterization of epitaxial YBaFormula: see textCuFormula: see textOFormula: see text (YBCO) complex oxide thin films and related heterostructures exclusively by Pulsed ...Laser Deposition (PLD) and using first harmonic Nd:YFormula: see textAlFormula: see textOFormula: see text (Nd:YAG) pulsed laser source (Formula: see text = 1064 nm). High-quality epitaxial YBCO thin film heterostructures display superconducting properties with transition temperature Formula: see text 80 K. Compared with the excimer lasers, when using Nd:YAG lasers, the optimal growth conditions are achieved at a large target-to-substrate distance d. These results clearly demonstrate the potential use of the first harmonic Nd:YAG laser source as an alternative to the excimer lasers for the PLD thin film community. Its compactness as well as the absence of any safety issues related to poisonous gas represent a major breakthrough in the deposition of complex multi-element compounds in form of thin films.
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