16,227 research outputs found
-cation control of magnetoelectric quadrupole order in (TiO)Cu(PO) ( = Ba, Sr, and Pb)
Ferroic magnetic quadrupole order exhibiting macroscopic magnetoelectric
activity is discovered in the novel compound (TiO)Cu(PO) with
= Pb, which is in contrast with antiferroic quadrupole order observed in
the isostructural compounds with = Ba and Sr. Unlike the famous lone-pair
stereochemical activity which often triggers ferroelectricity as in PbTiO,
the Pb cation in Pb(TiO)Cu(PO) is stereochemically inactive
but dramatically alters specific magnetic interactions and consequently
switches the quadrupole order from antiferroic to ferroic. Our first-principles
calculations uncover a positive correlation between the degree of -O bond
covalency and a stability of the ferroic quadrupole order.Comment: 7 pages, 4 figure
Stochastic delocalization of finite populations
Heterogeneities in environmental conditions often induce corresponding
heterogeneities in the distribution of species. In the extreme case of a
localized patch of increased growth rates, reproducing populations can become
strongly concentrated at the patch despite the entropic tendency for population
to distribute evenly. Several deterministic mathematical models have been used
to characterize the conditions under which localized states can form, and how
they break down due to convective driving forces. Here, we study the
delocalization of a finite population in the presence of number fluctuations.
We find that any finite population delocalizes on sufficiently long time
scales. Depending on parameters, however, populations may remain localized for
a very long time. The typical waiting time to delocalization increases
exponentially with both population size and distance to the critical wind speed
of the deterministic approximation. We augment these simulation results by a
mathematical analysis that treats the reproduction and migration of individuals
as branching random walks subject to global constraints. For a particular
constraint, different from a fixed population size constraint, this model
yields a solvable first moment equation. We find that this solvable model
approximates very well the fixed population size model for large populations,
but starts to deviate as population sizes are small. The analytical approach
allows us to map out a phase diagram of the order parameter as a function of
the two driving parameters, inverse population size and wind speed. Our results
may be used to extend the analysis of delocalization transitions to different
settings, such as the viral quasi-species scenario
Anisotropic Electronic Structure of the Kondo Semiconductor CeFe2Al10 Studied by Optical Conductivity
We report temperature-dependent polarized optical conductivity
[] spectra of CeFeAl, which is a reference material
for CeRuAl and CeOsAl with an anomalous magnetic
transition at 28 K. The spectrum along the b-axis differs
greatly from that in the -plane, indicating that this material has an
anisotropic electronic structure. At low temperatures, in all axes, a shoulder
structure due to the optical transition across the hybridization gap between
the conduction band and the localized states, namely -
hybridization, appears at 55 meV. However, the gap opening temperature and the
temperature of appearance of the quasiparticle Drude weight are strongly
anisotropic indicating the anisotropic Kondo temperature. The strong
anisotropic nature in both electronic structure and Kondo temperature is
considered to be relevant the anomalous magnetic phase transition in
CeRuAl and CeOsAl.Comment: 5 pages, 4 figure
Novel ordering of an S = 1/2 quasi one-dimensional Ising-like anitiferromagnet in magnetic field
High-field specific heat measurements on BaCo2V2O8, which is a good
realization of an S = 1/2 quasi one-dimensional Ising-like antifferomagnet,
have been performed in magnetic fields up to 12 T along the chain and at
temperature down to 200 mK. We have found a new magnetic ordered state in the
field-induced phase above Hc ~ 3.9 T. We suggest that a novel type of the
incommensurate order, which has no correspondence to the classical spin system,
is realized in the field-induced phase.Comment: 4pages, 4figure
Non-holomorphic multi-matrix gauge invariant operators based on Brauer algebra
We present an orthogonal basis of gauge invariant operators constructed from
some complex matrices for the free matrix field, where operators are expressed
with the help of Brauer algebra. This is a generalisation of our previous work
for a signle complex matrix. We also discuss the matrix quantum mechanics
relevant to N=4 SYM on S^{3} times R. A commuting set of conserved operators
whose eigenstates are given by the orthogonal basis is shown by using enhanced
symmetries at zero coupling.Comment: 29 pages, typos corrected, references adde
Universality and Critical Behavior at the Critical-End-Point on Itinerant-Metamagnet UCoAl
We performed nuclear-magnetic-resonance (NMR) measurements on
itinerant-electron metamagnet UCoAl in order to investigate the critical
behavior of the magnetism near a metamagnetic (MM) critical endpoint (CEP). We
derived c-axis magnetization and its fluctuation from the
measurements of Knight shift and nuclear spin-lattice relaxation rate
as a function of the c-axis external field () and temperature (). We
developed contour plots of and on the - phase diagram,
and observed the strong divergence of at the CEP. The critical exponents
of and near the CEP are estimated, and found to be close to the
universal properties of a three-dimensional (3-D) Ising model. We indicate that
the critical phenomena at the itinerant-electron MM CEP in UCoAl have a common
feature as a gas-liquid transition.Comment: 8 Pages, 14 figure
Ultrafast Acousto-Plasmonics in Gold Nanoparticles Superlattice
We report the investigation of the generation and detection of GHz coherent
acoustic phonons in plasmonic gold nanoparticles superlattices (NPS). The
experiments have been performed from an optical femtosecond pump-probe scheme
across the optical plasmon resonance of the superlattice. Our experiments allow
to estimate the collective elastic response (sound velocity) of the NPS as well
as an estimate of the nano-contact elastic stiffness. It appears that the
light-induced coherent acoustic phonon pulse has a typical in-depth spatial
extension of about 45 nm which is roughly 4 times the optical skin depth in
gold. The modeling of the transient optical reflectivity indicates that the
mechanism of phonon generation is achieved through ultrafast heating of the NPS
assisted by light excitation of the volume plasmon. These results demonstrate
how it is possible to map the photon-electron-phonon interaction in
subwavelength nanostructures
The epidemiology of clostridium difficile infection in Japan: A systematic review
To increase understanding of the epidemiology, risks, consequences and resource utilization of Clostridium difficile infection (CDI) in Japan, a systematic literature review was undertaken of relevant publications from January 2006 to November 2017. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and methods, 55 articles met the criteria for full review. The majority (58%) of studies were from a single site, with the most recent data from 2015. The incidence, reported prevalence and recurrence rate of CDI in Japan were 0.8–4.71/10,000 patient-days, 0.3–5.5/1000 patients and 3.3–27.3%, respectively, and varied according to setting, population, CDI definition and detection method. Most C. difficile isolates associated with CDI in Japan were toxin A+B+, with a low level of C. difficile binary toxin-positive (CDT+) strains (0–6.8% reported across studies). The most common C. difficile PCR ribotypes associated with infection in Japan were smz/018, 002, 052 and 369. Data regarding the impact of CDI on length of hospital stay were limited. Reported all-cause mortality in patients with CDI ranged from 3.4 to 15.1% between 2007 and 2013. Two studies assessed risk factors for CDI recurrence, identifying malignant disease, intensive care unit hospitalization and use of proton pump inhibitors as factors increasing the risk of initial and/or recurrent CDI. No study analyzed initial CDI treatment in relation to recurrence. More comprehensive surveillance and coordinated studies are needed to map trends, understand risk factors, and recognize the extent and impact of CDI in Japanese patients
Optical study of archetypical valence-fluctuating Eu-systems
We have investigated the optical conductivity of the prominent valence
fluctuating compounds EuIr2Si2 and EuNi2P2 in the infrared energy range to get
new insights into the electronic properties of valence fluctuating systems. For
both compounds we observe upon cooling the formation of a renormalized Drude
response, a partial suppression of the optical conductivity below 100 meV and
the appearance of a mid-infrared peak at 0.15 eV for EuIr2Si2 and at 0.13 eV
for EuNi2P2. Most remarkably, our results show a strong similarity with the
optical spectra reported for many Ce- or Yb-based heavy fermion metals and
intermediate valence systems, although the phase diagrams and the temperature
dependence of the valence differ strongly between Eu- and Ce-/Yb-systems. This
suggests that the hybridization between 4f- and conduction electrons, which is
responsible for the properties of Ce- and Yb-systems, plays an important role
in valence fluctuating Eu-systems
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