1,064 research outputs found
Sharp lines in the absorption edge of EuTe and PbEuTe in high magnetic fields
The optical absorption spectra in the region of the \fd transition energies
of epitaxial layers of of EuTe and \PbEuTe, grown by molecular beam epitaxy,
were studied using circularly polarized light, in the Faraday configuration.
Under \sigmam polarization a sharp symmetric absorption line (full width at
half-maximum 0.041 eV) emerges at the low energy side of the band-edge
absorption, for magnetic fields intensities greater than 6 T. The absorption
line shows a huge red shift (35 meV/T) with increasing magnetic fields. The
peak position of the absorption line as a function of magnetic field is
dominated by the {\em d-f} exchange interaction of the excited electron and the
\Euion spins in the lattice. The {\em d-f} exchange interaction energy was
estimated to be eV. In \PbEuTe the same absorption line
is detected, but it is broader, due to alloy disorder, indicating that the
excitation is localized within a finite radius. From a comparison of the
absorption spectra in EuTe and \PbEuTe the characteristic radius of the
excitation is estimated to be \AA.Comment: Journal of Physics: Condensed Matter (2004, at press
Spin-polarized tunneling currents through a ferromagnetic insulator between two metallic or superconducting leads
Using the Keldysh formalism the tunneling current through a hybrid structure
where a confined magnetic insulator (I) is sandwiched between two non-magnetic
leads is calculated. The leads can be either normal metals (M) or
superconductors (S). Each region is modelled as a single band in tight-binding
approximation in order to understand the formation of the tunneling current as
clearly as possible. The tunneling process itself is simulated by a
hybridization between the lead and insulator conduction bands. The insulator is
assumed to have localized moments which can interact with the tunneling
electrons. This is described by the Kondo Lattice Model (KLM) and treated
within an interpolating self-energy approach. For the superconductor the
mean-field BCS theory is used. The spin polarization of the current shows a
strong dependence both on the applied voltage and the properties of the
materials. Even for this idealized three band model there is a qualitative
agreement with experiment.Comment: 15 pages, 23 figures, accepted for publication in PR
ReaktivitĂ€t der Metall-Metall-Mehrfachbindung in Ăbergangsmetall-Komplexen: XIV. Reaktion von Cp*2CoRh(ÎŒ-CO)2 (Cp* = η5-C5Me5) mit Schwefel oder Selen und MolkĂŒlstruktur von Cp*2CoRh(CO)2(ÎŒ-Se)2
ReaktivitĂ€tsstudien an S- und Se-verbrĂŒckten zweikernigen Carbonyl-Rhodium-Komplexen ( = REACTIVITY OF DINUCLEAR S-BRIDGED AND SE-BRIDGED CARBONYL-RHODIUM COMPLEXES)
Electron rescattering at metal nanotips induced by ultrashort laser pulses
We report on the first investigation of plateau and cut-off structures in
photoelectron spectra from nano-scale metal tips interacting with few-cycle
near-infrared laser pulses. These hallmarks of electron rescattering,
well-known from atom-laser interaction in the strong-field regime, appear at
remarkably low laser intensities with nominal Keldysh parameters of the order
of . Quantum and quasi-classical simulations reveal that a large
field enhancement near the tip and the increased backscattering probability at
a solid-state target play a key role. Plateau electrons are by an order of
magnitude more abundant than in comparable atomic spectra, reflecting the high
density of target atoms at the surface. The position of the cut-off serves as
an in-situ probe for the locally enhanced electric field at the tip apex
Rural Teachersâ Burnout, Well-Being, and COVID-19 Related Stress During the Pandemic
To date, researchers have not explored the impact of the COVID-19 pandemic on the well-being of rural teachers specifically. Rural schools already faced long-standing issues of lower salaries, professional isolation, teacher shortages, and technology challenges, suggesting rural teachers may have experienced even higher levels of distress due to the pandemic. Overall, however, teachers from one rural county school system in the southeastern United States reported moderate COVID-19 concerns, low distress, and moderate well-being. Results could reflect responses characteristic of rural resilience. Further study is needed to explore teachersâ unique coping strategies
A nearly symmetric double-image gravitational lens
We report the discovery of a new double-image gravitational lens resulting
from our search for lenses in the southern sky. Radio source PMN J2004-1349 is
composed of two compact components separated by 1.13 arcseconds in VLA, MERLIN
and VLBA images. The components have a flux ratio of 1:1 at radio frequencies
ranging from 5 GHz to 22 GHz. The I-band optical counterpart is also an equal
double, with roughly the same separation and position angle as the radio
double. Upon subtraction of the components from the I-band image, we identify a
dim pattern of residuals as the lens galaxy. While the present observations are
sufficient to establish that J2004-1349 is a gravitational lens, additional
information will be necessary (such as the redshifts of the galaxy and quasar,
and precise astrometry and photometry of the lens galaxy) before constructing
detailed mass models.Comment: 17 pp., 5 bitmapped figs. (contact [email protected] for nicer figs), in
press, A.J. (substantially revised
Dynamics and transport properties of heavy fermions: theory
The paramagnetic phase of heavy fermion systems is investigated, using a
non-perturbative local moment approach to the asymmetric periodic Anderson
model within the framework of dynamical mean field theory. The natural focus is
on the strong coupling Kondo-lattice regime wherein single-particle spectra,
scattering rates, dc transport and optics are found to exhibit w/w_L,T/w_L
scaling in terms of a single underlying low-energy coherence scale w_L.
Dynamics/transport on all relevant (w,T)-scales are encompassed, from the
low-energy behaviour characteristic of the lattice coherent Fermi liquid,
through incoherent effective single-impurity physics likewise found to arise in
the universal scaling regime, to non-universal high-energy scales; and which
description in turn enables viable quantitative comparison to experiment.Comment: 27 pages, 12 figure
Optical study of the electronic phase transition of strongly correlated YbInCu_4
Infrared, visible and near-UV reflectivity measurements are used to obtain
conductivity as a function of temperature and frequency in YbInCu_4, which
exhibits an isostructural phase-transition into a mixed-valent phase below
T_v=42 K. In addition to a gradual loss of spectral weight with decreasing
temperature extending up to 1.5 eV, a sharp resonance appears at 0.25 eV in the
mixed-valent phase. This feature can be described in terms of excitations into
the Kondo (Abrikosov-Suhl) resonance, and, like the sudden reduction of
resistivity, provides a direct reflection of the onset of coherence in this
strongly correlated electron system.Comment: 4 pages, 3 figures (to appear in Phys. Rev. B
Interprofessional communication with hospitalist and consultant physicians in general internal medicine : a qualitative study
This study helps to improve our understanding of the collaborative environment in GIM, comparing the communication styles and strategies of hospitalist and consultant physicians, as well as the experiences of providers working with them. The implications of this research are globally important for understanding how to create opportunities for physicians and their colleagues to meaningfully and consistently participate in interprofessional communication which has been shown to improve patient, provider, and organizational outcomes
- âŠ