196 research outputs found
Tunable two-dimensional electron system at the (110) surface of SnO
We report the observation of a two-dimensional electron system (2DES) at the
surface of the transparent bulk insulator SnO, and the tunability
of its carrier density by means of temperature or Eu deposition. The 2DES is
insensitive to surface reconstructions and, surprisingly, it survives even
after exposure to ambient conditions --an extraordinary fact recalling the well
known catalytic properties SnO. Our data show that surface oxygen vacancies
are at the origin of such 2DES, providing key information about the
long-debated origin of -type conductivity in SnO, at the basis of a wide
range of applications. Furthermore, our study shows that the emergence of a
2DES in a given oxide depends on a delicate interplay between its crystal
structure and the orbital character of its conduction band.Comment: 11 pages, 12 figure
Electronic reconstruction forming a -symmetric Dirac semimetal in CaRuO
Electronic band structures in solids stem from a periodic potential
reflecting the structure of either the crystal lattice or an electronic order.
In the stoichiometric ruthenate CaRuO, numerous Fermi surface
sensitive probes indicate a low-temperature electronic reconstruction. Yet, the
causality and the reconstructed band structure remain unsolved. Here, we show
by angle-resolved photoemission spectroscopy, how in CaRuO a
-symmetric massive Dirac semimetal is realized through a Brillouin-zone
preserving electronic reconstruction. This Dirac semimetal emerges in a
two-stage transition upon cooling. The Dirac point and band velocities are
consistent with constraints set by quantum oscillation, thermodynamic, and
transport experiments, suggesting that the complete Fermi surface is resolved.
The reconstructed structure -- incompatible with
translational-symmetry-breaking density waves -- serves as an important test
for band structure calculations of correlated electron systems
Revealing the Orbital Composition of Heavy Fermion Quasiparticles in CeRu2Si2
We present a resonant angle-resolved photoemission spectroscopy (ARPES) study of the electronic band structure and heavy fermion quasiparticles in CeRu2Si2. Using light polarization analysis, considerations of the crystal field environment and hybridization between conduction and f electronic states, we identify the d-electronic orbital character of conduction bands crossing the Fermi level. Resonant ARPES spectra suggest that the localized Ce f states hybridize with eg and t2g states around the zone center. In this fashion, we reveal the orbital structure of the heavy fermion quasiparticles in CeRu2Si2 and discuss its implications for metamagnetism and superconductivity in the related compound CeCu2Si2
Observation by resonant angle-resolved photoemission of a critical thickness for 2-dimensional electron gas formation in SrTiO embedded in GdTiO
For certain conditions of layer thickness, the interface between GdTiO
(GTO) and SrTiO (STO) in multilayer samples has been found to form a
two-dimensional electron gas (2DEG) with very interesting properties including
high mobilities and ferromagnetism. We have here studied two trilayer samples
of the form [2 nm GTO/1.0 or 1.5 unit cells STO/10 nm GTO] as grown on (001)
(LaAlO)(SrAlTaO) (LSAT), with the STO layer
thicknesses being at what has been suggested is the critical thickness for 2DEG
formation. We have studied these with Ti-resonant angle-resolved (ARPES) and
angle-integrated photoemission and find that the spectral feature in the
spectra associated with the 2DEG is present in the 1.5 unit cell sample, but
not in the 1.0 unit cell sample. We also observe through core-level spectra
additional states in Ti and Sr, with the strength of a low-binding-energy state
for Sr being associated with the appearance of the 2DEG, and we suggest it to
have an origin in final-state core-hole screening.Comment: 12 pages, 4 figure
ELSA in industrial robotics
Purpose of ReviewIndustry is changing; converging technologies allow a fourth Industrial Revolution, where it is envisaged that robots will work alongside humans. We investigate how the research community is responding to the ethical, legal, and social aspects of industrial robots, with a primary focus on manufacturing industry.Recent FindingsThe literature shows considerable interest in the impact of robotics and automation on industry. This interest spans many disciplines, which is to be expected given that the ELS impacts of industrial robotics may be profound in their depth and far-reaching in their scope.SummaryWe suggest that the increasing importance of human-robot interaction (HRI) reduces the differentiation between industrial robotics and other robotic domains and that the main challenges to successful adoption for the benefit of human life are above all political and economic. Emerging standards and legal frameworks may scaffold this success, but it is apparent that getting it wrong might have repercussions that last for generations
Photoemission signature of momentum-dependent hybridization in CeCoIn5
Hybridization between f electrons and conduction bands (c-f hybridization) is a driving force for many unusual phenomena. To provide insight into it, systematic studies of CeCoIn 5 heavy fermion superconductor have been performed by angle-resolved photoemission spectroscopy (ARPES) in a large angular range at temperature of T = 6 K. The used photon energy of 122 eV corresponds to Ce 4d-4f resonance. Calculations carried out with the relativistic multiple scattering Korringa-Kohn-Rostoker method and one-step model of photoemission yielded realistic simulation of the ARPES spectra, indicating that Ce-In surface termination prevails. Surface states, which have been identified in the calculations, contribute significantly to the spectra. Effects of the hybridization strongly depend on wave vector. They include a dispersion of heavy electrons and bands gaining f-electron character when approaching Fermi energy. We have also observed a considerable variation of f-electron spectral weight at EF , which is normally determined by both matrix element effects and wave vector dependent c-f hybridization. Fermi surface scans covering a few Brillouin zones revealed large matrix element effects. A symmetrization of experimental Fermi surface, which reduces matrix element contribution, yielded a specific variation of 4f-electron enhanced spectral intensity at EF around Gamma barre and M barre points. Tight-binding approximation calculations for Ce-In plane provided the same universal distribution of 4f-electron density for a range of values of the parameters used in the model
Quantitative Evaluation of Scintillation Camera Imaging Characteristics of Isotopes Used in Liver Radioembolization
Scintillation camera imaging is used for treatment planning and post-treatment dosimetry in liver radioembolization (RE). In yttrium-90 (90Y) RE, scintigraphic images of technetium-99m (99mTc) are used for treatment planning, while 90Y Bremsstrahlung images are used for post-treatment dosimetry. In holmium-166 (166Ho) RE, scintigraphic images of 166Ho can be used for both treatment planning and post-treatment dosimetry. The aim of this study is to quantitatively evaluate and compare the imaging characteristics of these three isotopes, in order that imaging protocols can be optimized and RE studies with varying isotopes can be compared.Phantom experiments were performed in line with NEMA guidelines to assess the spatial resolution, sensitivity, count rate linearity, and contrast recovery of 99mTc, 90Y and 166Ho. In addition, Monte Carlo simulations were performed to obtain detailed information about the history of detected photons. The results showed that the use of a broad energy window and the high-energy collimator gave optimal combination of sensitivity, spatial resolution, and primary photon fraction for 90Y Bremsstrahlung imaging, although differences with the medium-energy collimator were small. For 166Ho, the high-energy collimator also slightly outperformed the medium-energy collimator. In comparison with 99mTc, the image quality of both 90Y and 166Ho is degraded by a lower spatial resolution, a lower sensitivity, and larger scatter and collimator penetration fractions.The quantitative evaluation of the scintillation camera characteristics presented in this study helps to optimize acquisition parameters and supports future analysis of clinical comparisons between RE studies
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