1,052 research outputs found
Contrast of LiFeAs with isostructural, isoelectronic, and non-superconducting MgFeGe
Stoichiometric LiFeAs at ambient pressure is an 18 K superconductor while
isoelectronic MgFeGe is not, despite their extremely similar electronic
structures. To investigate possible sources of this distinctively different
superconducting behavior, we quantify the differences using first principles
density functional theory, establishing first that the Fe total 3d occupations
are identical in the two compounds. Individual 3d orbital occupations also
differ very little (). The differences in Fermi surfaces (FSs) do
not seem significant; however a redistribution of bands just above the Fermi
level does represent a possibly significant distinction. Because the bands and
FSs of LiFeAs are less in agreement with experiment than for other
iron-pnictides, we study the effects of additional exchange-correlations
effects beyond GGA (the generalized gradient approximation) by applying the
modified Becke-Johnson potential (mBJ) exchange potential, which gives much
improved bandgaps in insulators compared to GGA and might be useful for
semimetals such as the Fe-based superconductors. Overall, we conclude that the
mBJ corrections do not improve the description of LiFeAs as compared to
experiment
Engineering surface states of carbon dots to achieve controllable luminescence for solid-luminescent composites and sensitive Be2+ detection
Luminescent carbon dots (L-CDs) with high quantum yield value (44.7%) and controllable emission wavelengths were prepared via a facile hydrothermal method. Importantly, the surface states of the materials could be engineered so that their photoluminescence was either excitation-dependent or distinctly independent. This was achieved by changing the density of amino-groups on the L-CD surface. The above materials were successfully used to prepare multicolor L-CDs/polymer composites, which exhibited blue, green, and even white luminescence. In addition, the excellent excitation-independent luminescence of L-CDs prepared at low temperature was tested for detecting various metal ions. As an example, the detection limit of toxic Be2+ ions, tested for the first time, was as low as μM
A Comparative Study on the Nonlinear Interaction Between a Focusing Wave and Cylinder Using State-of-the-art Solvers: Part A
This paper presents ISOPE’s 2020 comparative study on the interaction between focused waves and a fixed cylinder. The paper discusses the qualitative and quantitative comparisons between 20 different numerical solvers from various universities across the world for a fixed cylinder. The moving cylinder cases are reported in a companion paper as part B (Agarwal, Saincher, et al., 2021). The numerical solvers presented in this paper are the recent state of the art in the field, mostly developed in-house by various academic institutes. The majority of the participants used hybrid modeling (i.e., a combination of potential flow and Navier–Stokes solvers). The qualitative comparisons based on the wave probe and pressure probe time histories and spectral components between laminar, turbulent, and potential flow solvers are presented in this paper. Furthermore, the quantitative error analyses based on the overall relative error in peak and phase shifts in the wave probe and pressure probe of all the 20 different solvers are reported. The quantitative errors with respect to different spectral component energy levels (i.e., in primary, sub-, and superharmonic regions) capturing capability are reported. Thus, the paper discusses the maximum, minimum, and median relative errors present in recent solvers as regards application to industrial problems rather than attempting to find the best solver. Furthermore, recommendations are drawn based on the analysis
A New Look at the Scalar Meson via Decays
Using of collision data collected with the
BESIII detector at the center-of-mass energy of 3.773 GeV, we investigate the
semileptonic decays ( and ).
The decay is observed for the first time. By
analyzing simultaneously the differential decay rates of and in different
four-momentum transfer intervals, the product of the relevant hadronic form
factor and the magnitude of the
Cabibbo-Kobayashi-Maskawa matrix element is determined to be
for
the first time. With the input of from the global fit in the
standard model, we determine . The absolute branching fractions of and are determined as and . Combining these results with those of previous BESIII measurements on
their semielectronic counterparts from the same data sample, we test lepton
flavor universality by measuring the branching fraction ratios and , which are
compatible with the standard model expectation.Comment: Supplemental Materials added in this versio
Study of the doubly Cabibbo-suppressed decays and
Based on 7.33 fb of collision data collected at
center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector,
the experimental studies of the doubly Cabibbo-suppressed decays and are reported. We determine the
absolute branching fraction of to be
() . No
significant signal of is observed and the upper
limit on its decay branching fraction at 90\% confidence level is set to be
.Comment: 10 pages, 4 figures, 4 table
Search for an invisible muon philic scalar or vector via decay at BESIII
A light scalar or vector particles have been introduced as a
possible explanation for the anomaly and dark matter phenomena.
Using \jpsi events collected by the BESIII
detector, we search for a light muon philic scalar or vector in
the processes with invisible decays. No
obvious signal is found, and the upper limits on the coupling
between the muon and the particles are set to be between
and for the mass in the range
of ~MeV at 90 confidence level.Comment: 9 pages 7 figure
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