69 research outputs found
The agent provocateur in the labour movement
https://stars.library.ucf.edu/prism/1684/thumbnail.jp
Dynamic Shear Rheometer Testing of Asphalt Binder using 4 mm parallel plate geometry at low temperature: 2nd Interlaboratory Study including test results of 16 participating laboratories from Austria, Belgium, Czech Republic, France, Germany, Italy, Lithuania, Poland, and Sweden ; Final Report
PrĂ€diktion der Ăberlebenswahrscheinlichkeit mit Dummys und Menschmodellen bei FahrzeugunfĂ€llen
Tailoring Plasmonics of Au@Ag Nanoparticles by Silica Encapsulation
Hybrid metallic nanoparticles encapsulated in oxide shells are currently
intensely studied for plasmonic applications in sensing, medicine, catalysis,
and photovoltaics. Here, we introduce a method for the synthesis of
Au@Ag@SiO cubes with a uniform silica shell of variable and adjustable
thickness in the nanometer range; and we demonstrate their excellent, highly
reproducible, and tunable optical response. Varying the silica shell thickness,
we could tune the excitation energies of the single nanoparticle plasmon modes
in a broad spectral range between 2.55 and 3.25\,eV. Most importantly, we
reveal a strong coherent coupling of the surface plasmons at the silver-silica
interface with the whispering gallery resonance at the silica-vacuum interface
leading to a significant field enhancement at the encapsulated nanoparticle
surface in the range of 100\,\% at shell thicknesses 20\,nm.
Consequently, the synthesis method and the field enhancement open pathways to a
widespread use of silver nanoparticles in plasmonic applications including
photonic crystals and may be transferred to other non-precious metals
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Axion Mie theory of electron energy loss spectroscopy in topological insulators
Electronic topological states of matter exhibit novel types of responses to electromagnetic fields. The response of strong topological insulators, for instance, is characterized by a so-called axion term in the electromagnetic Lagrangian which is ultimately due to the presence of topological surface states. Here we develop the axion Mie theory for the electromagnetic response of spherical particles including arbitrary sources of fields, i.e., charge and current distributions. We derive an axion induced mixing of transverse magnetic and transverse electric modes which are experimentally detectable through small induced rotations of the field vectors. Our results extend upon previous analyses of the problem. Our main focus is on the experimentally relevant problem of electron energy loss spectroscopy in topological insulators, a technique that has so far not yet been used to detect the axion electromagnetic response in these materials
Suppression of the magnetic order in CeFeAsO: non-equivalence of hydrostatic and chemical pressure
We present a detailed investigation of the electronic properties of CeFeAsO
under chemical (As by P substitution) and hydrostatic pressure by means of
in-house and synchrotron M\"ossbauer spectroscopy. The Fe magnetism is
suppressed due to both pressures and no magnetic order was observed above a
P-substitution level of 40% or 5.2 GPa hydrostatic pressure. We compared both
pressures and found that the isovalent As by P substitution change the
crystallographic and electronic properties differently than hydrostatic
pressure.Comment: supplement is included in the pdf fil
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Disorder-induced coupling of Weyl nodes in WTe2
The finite coupling between Weyl nodes due to residual disorder is investigated by magnetotransport studies in WTe2. The anisotropic scattering of quasiparticles is evidenced from classical and quantum transport measurements. A theoretical approach using the real band structure is developed in order to calculate the dependence of the scattering anisotropy with the correlation length of the disorder. A comparison between theory and experiments reveals a short correlation length in WTe2 (ΟâŒ5 nm). This result implies a significant coupling between Weyl nodes and other bands. Our study thus shows that a finite intercone scattering rate always exists in weakly disordered type-II Weyl semimetals, such as WTe2, which strongly suppresses topologically nontrivial properties
Electronic structure of undoped and potassium doped coronene investigated by electron energy-loss spectroscopy
We performed electron energy-loss spectroscopy studies in transmission in
order to obtain insight into the electronic properties of potassium
intercalated coronene, a recently discovered superconductor with a rather high
transition temperature of about 15\,K. A comparison of the loss function of
undoped and potassium intercalated coronene shows the appearance of several new
peaks in the optical gap upon potassium addition. Furthermore, our core level
excitation data clearly signal filling of the conduction bands with electrons.Comment: 15 pages, 5 figures. arXiv admin note: substantial text overlap with
arXiv:1102.328
Bereziskii-Kosterlitz-Thouless transition in the Weyl system \ce{PtBi2}
Symmetry breaking in topological matter became, in the last decade, a key
concept in condensed matter physics to unveil novel electronic states. In this
work, we reveal that broken inversion symmetry and strong spin-orbit coupling
in trigonal \ce{PtBi2} lead to a Weyl semimetal band structure, with unusually
robust two-dimensional superconductivity in thin fims. Transport measurements
show that high-quality \ce{PtBi2} crystals are three-dimensional
superconductors (600~mK) with an isotropic critical field
(50~mT). Remarkably, we evidence in a rather thick flake
(60~nm), exfoliated from a macroscopic crystal, the two-dimensional nature of
the superconducting state, with a critical temperature ~mK and highly-anisotropic critical fields. Our results reveal a
Berezinskii-Kosterlitz-Thouless transition with ~mK and
with a broadening of Tc due to inhomogenities in the sample. Due to the very
long superconducting coherence length in \ce{PtBi2}, the
vortex-antivortex pairing mechanism can be studied in unusually-thick samples
(at least five times thicker than for any other two-dimensional
superconductor), making \ce{PtBi2} an ideal platform to study low dimensional
superconductivity in a topological semimetal
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