5,129 research outputs found
Neutron transition strengths of states in the neutron rich Oxygen isotopes determined from inelastic proton scattering
A coupled-channel analysis of the O data has been
performed to determine the neutron transition strengths of 2 states in
Oxygen targets, using the microscopic optical potential and inelastic form
factor calculated in the folding model. A complex density- and \emph{isospin}
dependent version of the CDM3Y6 interaction was constructed, based on the
Brueckner-Hatree-Fock calculation of nuclear matter, for the folding model
input. Given an accurate isovector density dependence of the CDM3Y6
interaction, the isoscalar () and isovector () deformation
lengths of 2 states in O have been extracted from the
folding model analysis of the data. A specific -dependence of
and has been established which can be linked to the
neutron shell closure occurring at approaching 16. The strongest isovector
deformation was found for 2 state in O, with about 2.5
times larger than , which indicates a strong core polarization by the
valence neutrons in O. The ratios of the neutron/proton transition
matrix elements () determined for 2 states in O have
been compared to those deduced from the mirror symmetry, using the measured
values of 2 states in the proton rich Ne and Mg
nuclei, to discuss the isospin impurity in the excitation of the
and isobars.Comment: Version accepted for publication in Physical Review
Pair formation and collapse in imbalanced Fermion populations with unequal masses
We present an exact Quantum Monte Carlo study of the effect of unequal masses
on pair formation in Fermionic systems with population imbalance loaded into
optical lattices. We have considered three forms of the attractive interaction
and find in all cases that the system is unstable and collapses as the mass
difference increases and that the ground state becomes an inhomogeneous
collapsed state. We also address the question of canonical vs grand canonical
ensemble and its role, if any, in stabilizing certain phases
Analytical approximation for the sphere-sphere Coulomb potential
A simple analytical expression, which closely approximates the Coulomb
potential between two uniformly charged spheres, is presented. This expression
can be used in the optical potential semiclassical analyses which require that
the interaction be analytic on and near the real r-axis.Comment: 4 pages including 3 figures and 1 tabl
Atomic lattice excitons: from condensates to crystals
We discuss atomic lattice excitons (ALEs), bound particle-hole pairs formed
by fermionic atoms in two bands of an optical lattice. Such a system provides a
clean setup to study fundamental properties of excitons, ranging from
condensation to exciton crystals (which appear for a large effective mass ratio
between particles and holes). Using both mean-field treatments and 1D numerical
computation, we discuss the properities of ALEs under varying conditions, and
discuss in particular their preparation and measurement.Comment: 19 pages, 15 figures, changed formatting for journal submission,
corrected minor errors in reference list and tex
Optothermotronic effect as an ultrasensitive thermal sensing technology for solid-state electronics
The thermal excitation, regulation, and detection of charge carriers in solid-state electronics have attracted great attention toward high-performance sensing applications but still face major challenges. Manipulating thermal excitation and transport of charge carriers in nanoheterostructures, we report a giant temperature sensing effect in semiconductor nanofilms via optoelectronic coupling, termed optothermotronics. A gradient of charge carriers in the nanofilms under nonuniform light illumination is coupled with an electric tuning current to enhance the performance of the thermal sensing effect. As a proof of concept, we used silicon carbide (SiC) nanofilms that form nanoheterostructures on silicon (Si). The sensing performance based on the thermal excitation of charge carriers in SiC is enhanced by at least 100 times through photon excitation, with a giant temperature coefficient of resistance (TCR) of up to −50%/K. Our findings could be used to substantially enhance the thermal sensing performance of solid-state electronics beyond the present sensing technologies
Understanding the performance increase of catalysts supported on N-functionalized carbon in PEMFC catalyst layers
Applying nitrogen-modified carbon support in PEMFCs has been attracting arising interest due to the resulting performance enhancement. In the present study, we attempt to uncover the origin and gain a deeper understanding of the different N-modification processes, whose influences are responsible for the performance improvement. By utilizing chemically modified Ketjenblack supports comprising altered fraction of N-functionalities, we investigate the underlying mechanism of the drastically reduced voltage losses under fuel cell operation conditions. In all, we demonstrate the key role of support modification induced by ammonia in strengthened support/ionomer interactions and alter physico-chemical properties of the carbon support contributing towards enhanced MEA performance. With the use of X-ray photoelectron spectroscopy (XPS), we show unambiguous evidences that not all N modified surfaces yield the desired performance increase. Rather, the latter depends on a complex interplay between different electrochemical parameter and catalyst properties. We want to emphasize the ionomer/support interaction as one important factor for enhanced ionomer distribution and present a prove of a direct interaction between the ionomers´ sidechains and N-functional groups of the support
A review of the MSCA ITN ECOSTORE - Novel complex metal hydrides for efficient and compact storage of renewable energy as hydrogen and electricity
Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel, sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However, there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+, Mg2+ and Ca2+, while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials, the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore, it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Skłodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE, the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed
Low temperature properties of the fermionic mixtures with mass imbalance in optical lattice
We study the attractive Hubbard model with mass imbalance to clarify low
temperature properties of the fermionic mixtures in the optical lattice. By
combining dynamical mean-field theory with the continuous-time quantum Monte
Carlo simulation, we discuss the competition between the superfluid and density
wave states at half filling. By calculating the energy and the order parameter
for each state, we clarify that the coexisting (supersolid) state, where the
density wave and superfluid states are degenerate, is realized in the system.
We then determine the phase diagram at finite temperatures.Comment: 5 pages, 4 figures, accepted for publication in J. Phys. Soc. Jp
Statefinder diagnostic for cosmology with the abnormally weighting energy hypothesis
In this paper, we apply the statefinder diagnostic to the cosmology with the
Abnormally Weighting Energy hypothesis (AWE cosmology), in which dark energy in
the observational (ordinary matter) frame results from the violation of weak
equivalence principle (WEP) by pressureless matter. It is found that there
exist closed loops in the statefinder plane, which is an interesting
characteristic of the evolution trajectories of statefinder parameters and can
be used to distinguish AWE cosmology from the other cosmological models.Comment: 5 pages, 4 figures, accepted by PR
Mass Dependence of M3Y-Type Interactions and the Effects of Tensor Correlations
The mass dependence of the M3Y-type effective interactions and the effects of
tensor correlations are examined. Two-body nuclear matrix elements are obtained
by the lowest order constrained variational (LOCV) technique with and without
tensor correlations. We have found that the tensor correlations are important
especially in the triplet-even (TE) and tensor-even (TNE) channels in order to
reproduce the G-matrix elements obtained previously. Then M3Y-type potentials
for inelastic scattering are obtained by fitting our two-body matrix elements
to those of a sum of Yukawa functions for the mass numbers A=24, A=40 and A=90.Comment: 13 pages, 6 table
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