1,425 research outputs found
Evidence for short-range antiferromagnetic fluctuations in Kondo-insulating YbB12
The spin dynamics of mixed-valence YbB12 has been studied by inelastic
neutron scattering on a high-quality single crystal. In the Kondo-insulating
regime realized at low temperature, the spectra exhibit a spin-gap structure
with two sharp, dispersive, in-gap excitations at E = 14.5 and approximately 20
meV. The lower mode is shown to be associated with short-range correlations
near the antiferromagnetic wave vector q0 = (1/2, 1/2, 1/2). Its properties are
in overall agreement with those expected for a "spin exciton'' branch in an
indirect hybridization gap semiconductor.Comment: 4 pages, 4 figures ; submitted to Physical Review Letter
Production delays, supply distortions and endogenous price dynamics
It takes time to produce commodities, and different production technologies may take different lengths of time. Suppose that firms may switch between different production technologies that take different lengths of time. A natural implication of such a scenario is that not all firms would then offer their commodities in every period, i.e. firms’ total
supply schedule would become a time-varying quantity. Based on a behavioral cobweb framework, we analytically demonstrate that commodity markets become unstable when firms switch too rapidly between production technologies that take different lengths of time. In particular, we observe that supply distortions lead to endogenous
commodity price dynamics due to a mismatch between supply and demand
Spontaneous deformation of the Fermi surface due to strong correlation in the two-dimensional t-J model
Fermi surface of the two-dimensional t-J model is studied using the
variational Monte Carlo method. We study the Gutzwiller projected d-wave
superconducting state with an additional variational parameter t'_v
corresponding to the next-nearest neighbor hopping term. It is found that the
finite t'_v<0 gives the lowest variational energy in the wide range of
hole-doping rates. The obtained momentum distribution function shows that the
Fermi surface deforms spontaneously. It is also shown that the van Hove
singularity is always located very close to the Fermi energy. Using the
Gutzwiller approximation, we show that this spontaneous deformation is due to
the Gutzwiller projection operator or the strong correlation.Comment: 4 pages, 3 eps figures, revte
The effect of uniaxial pressure on the magnetic anomalies of the heavy-fermion metamagnet CeRu2Si2
The effect of uniaxial pressure (P_u) on the magnetic susceptibility (X),
magnetization (M), and magnetoresistance (MR) of the heavy-fermion metamagnet
CeRu2Si2 has been investigated. For the magnetic field along the tetragonal c
axis, it is found that characteristic physical quantities, i.e., the
temperature of the susceptibility maximum (T_max), the pagamagnetic Weiss
temperature (Q_p), 1/X at 2 K, and the magnetic field of the metamagnetic
anomaly (H_M), scale approximately linearly with P_u, indicating that all the
quantities are related to the same energy scale, probably of the Kondo
temperature. The increase (decrease) of the quantities for P_u || c axis (P_u
|| a axis) can be attributed to a decrease (increase) in the nearest Ce-Ru
distance. Consistently in MR and X, we observed a sign that the anisotropic
nature of the hybridization, which is believed to play an important role in the
metamagnetic anomaly, can be controlled by applying the uniaxial pressure.
PACS numbers: 75.20.Hr, 71.27.+a, 74.62.FjComment: 7 pages, ReVTeX, 6 EPS figures : Will appear in Phys. Rev.
Glitter-like iridescence within the bacteroidetes especially Cellulophaga spp.: optical properties and correlation with gliding motility.
This is the final version of the article. Available from the publisher via the DOI in this record.Iridescence results from structures that generate color. Iridescence of bacterial colonies has recently been described and illustrated. The glitter-like iridescence class, created especially for a few strains of Cellulophaga lytica, exhibits an intense iridescence under direct illumination. Such color appearance effects were previously associated with other bacteria from the Bacteroidetes phylum, but without clear elucidation and illustration. To this end, we compared various bacterial strains to which the iridescent trait was attributed. All Cellulophaga species and additional Bacteroidetes strains from marine and terrestrial environments were investigated. A selection of bacteria, mostly marine in origin, were found to be iridescent. Although a common pattern of reflected wavelengths was recorded for the species investigated, optical spectroscopy and physical measurements revealed a range of different glitter-like iridescence intensity and color profiles. Importantly, gliding motility was found to be a common feature of all iridescent colonies. Dynamic analyses of "glitter" formation at the edges of C. lytica colonies showed that iridescence was correlated with layer superposition. Both gliding motility, and unknown cell-to-cell communication processes, may be required for the establishment, in time and space, of the necessary periodic structures responsible for the iridescent appearance of Bacteroidetes.PV acknowledges the support of AFOSR grant FA9550-10-1-0020. BK was a PhD student with a grant from the Ministe`re de la recherche et de
l’enseignement supe´rieur. ER acknowledges the support of CNRS grant AIR75515 (‘‘Bacte´ridescence’’ project). The funders had no role in study design, data
collection and analysis, decision to publish, or preparation of the manuscript
Pressure Evolution of the Magnetic Field induced Ferromagnetic Fluctuation through the Pseudo-Metamagnetism of CeRu2Si2
Resistivity measurements performed under pressure in the paramagnetic ground
state of CeRu2Si2 are reported. They demonstrate that the relative change of
effective mass through the pseudo metamagnetic transition is invariant under
pressure. The results are compared with the first order metamagnetic transition
due to the antiferromagnetism of Ce0.9La0.1Ru2Si2 which corresponds to the
"negative" pressure of CeRu2Si2 by volume expansion. Finally, we describe the
link between the spin-depairing of quasiparticles on CeRu2Si2 and that of
Cooper pairs on the unconventional heavy fermion superconductor CeCoIn5.Comment: 5 pages, 6 figures, accepted for publication in J. Phys. Soc. Jp
Multipole tensor analysis of the resonant x-ray scattering by quadrupolar and magnetic order in DyB2C2
Resonant x-ray scattering (RXS) experiment has been performed for the (3 0
1.5) superlattice reflection in the antiferroquadrupolar and antiferromagnetic
phase of DyB2C2. Azimuthal-angle dependence of the resonance enhanced
intensities for both dipolar (E1) and quadrupolar (E2) resonant processes has
been measured precisely with polarization analysis. Every scattering channel
exhibits distinctive azimuthal dependence, differently from the symmetric
reflection at (0 0 0.5) which was studied previously. We have analyzed the
results using a theory developed by Lovesey et al., which directly connects
atomic tensors with the cross-section of RXS. The fitting results indicate that
the azimuthal dependences can be explained well by the atomic tensors up to
rank 2. Rank 3 and rank 4 tensors are reflected in the data very little. In
addition, The coupling scheme among the 4f quadrupolar moment, 5d ortitals, and
the lattice has been determined from the interference among the Thomson
scattering from the lattice distortion and the resonant scatterings of E1 and
E2 processes. It has also been established from the RXS of the (3 0 1.5)
reflection that the canting of the 4f quadrupolar moments exists up to T_Q. We
also discuss a possible wavefunction of the ground state from the point-charge
model calculation.Comment: 9 pages, 10 figure
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