74 research outputs found
Optical and magneto-optical behavior of Cerium Yttrium Iron Garnet thin films at wavelengths of 200–1770 nm
Magneto-optical cerium-substituted yttrium iron garnet (Ce:YIG) thin films display Faraday and Kerr rotation (rotation of light polarisation upon transmission and reflection, respectively) as well as a nonreciprocal phase shift due to their non-zero off-diagonal permittivity tensor elements, and also possess low optical absorption in the near-infrared. These properties make Ce:YIG useful in providing nonreciprocal light propagation in integrated photonic circuits, which is essential for accomplishing energy-efficient photonic computation and data transport architectures. In this study, 80 nm-thick Ce:YIG films were grown on Gadolinium Gallium Garnet substrates with (100), (110) and (111) orientations using pulsed laser deposition. The films had bulk-like structural and magnetic quality. Faraday and Kerr spectroscopies along with spectroscopic ellipsometry were used to deduce the complete permittivity tensor of the films in the ultraviolet, visible and near-infrared spectral region, and the magneto-optical figure of merit as a function of wavelength was determined. The samples showed the highest IR Faraday rotation reported for thin films of Ce:YIG, which indicates the importance of this material in development of nonreciprocal photonic devices.National Science Foundation (U.S.)Semiconductor Research Corporation. Function Accelerated nanoMaterial Engineerin
Rigorous Analysis of Singularities and Absence of Analytic Continuation at First Order Phase Transition Points in Lattice Spin Models
We report about two new rigorous results on the non-analytic properties of
thermodynamic potentials at first order phase transition. The first one is
valid for lattice models () with arbitrary finite state space, and
finite-range interactions which have two ground states. Under the only
assumption that the Peierls Condition is satisfied for the ground states and
that the temperature is sufficiently low, we prove that the pressure has no
analytic continuation at the first order phase transition point. The second
result concerns Ising spins with Kac potentials
, where is a small scaling
parameter, and a fixed finite range potential. In this framework, we
relate the non-analytic behaviour of the pressure at the transition point to
the range of interaction, which equals . Our analysis exhibits a
crossover between the non-analytic behaviour of finite range models
() and analyticity in the mean field limit (). In
general, the basic mechanism responsible for the appearance of a singularity
blocking the analytic continuation is that arbitrarily large droplets of the
other phase become stable at the transition point.Comment: 4 pages, 2 figure
Mean-field driven first-order phase transitions in systems with long-range interactions
We consider a class of spin systems on with vector valued spins
(\bS_x) that interact via the pair-potentials J_{x,y} \bS_x\cdot\bS_y. The
interactions are generally spread-out in the sense that the 's exhibit
either exponential or power-law fall-off. Under the technical condition of
reflection positivity and for sufficiently spread out interactions, we prove
that the model exhibits a first-order phase transition whenever the associated
mean-field theory signals such a transition. As a consequence, e.g., in
dimensions , we can finally provide examples of the 3-state Potts model
with spread-out, exponentially decaying interactions, which undergoes a
first-order phase transition as the temperature varies. Similar transitions are
established in dimensions for power-law decaying interactions and in
high dimensions for next-nearest neighbor couplings. In addition, we also
investigate the limit of infinitely spread-out interactions. Specifically, we
show that once the mean-field theory is in a unique ``state,'' then in any
sequence of translation-invariant Gibbs states various observables converge to
their mean-field values and the states themselves converge to a product
measure.Comment: 57 pages; uses a (modified) jstatphys class fil
Fault orientations in the upper crust beneath an intraplate active zone in northern Egypt
Comparative morphology of the postpharyngeal gland in the Philanthinae (Hymenoptera, Crabronidae) and the evolution of an antimicrobial brood protection mechanism
SARS-CoV-2 Omicron-B.1.1.529 leads to widespread escape from neutralizing antibody responses
On 24th November 2021, the sequence of a new SARS-CoV-2 viral isolate Omicron-B.1.1.529 was announced, containing far more mutations in Spike (S) than previously reported variants. Neutralization titers of Omicron by sera from vaccinees and convalescent subjects infected with early pandemic Alpha, Beta, Gamma, or Delta are substantially reduced, or the sera failed to neutralize. Titers against Omicron are boosted by third vaccine doses and are high in both vaccinated individuals and those infected by Delta. Mutations in Omicron knock out or substantially reduce neutralization by most of the large panel of potent monoclonal antibodies and antibodies under commercial development. Omicron S has structural changes from earlier viruses and uses mutations that confer tight binding to ACE2 to unleash evolution driven by immune escape. This leads to a large number of mutations in the ACE2 binding site and rebalances receptor affinity to that of earlier pandemic viruses
Nucleophilic Substitution by a Hydroxide Ion at a Vinylic Carbon: Ab Initio and Density Functional Theory Studies on Methoxyethene, 3-Methoxypropenal, 2,3-Dihydro-4 H
Aportaciones al conocimiento del género Stagetus Wollaston, 1861 (Coleoptera, Ptinidae) en la península Ibérica
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