921 research outputs found
Observation of a Dirac nodal line in AlB2
We have performed angle-resolved photoemission spectroscopy of AlB2 which is
isostructural to high-temperature superconductor MgB2. Using soft-x-ray
photons, we accurately determined the three-dimensional bulk band structure and
found a highly anisotropic Dirac-cone band at the K point in the bulk hexagonal
Brillouin zone. This band disperses downward on approaching the H point while
keeping its degeneracy at the Dirac point, producing a characteristic Dirac
nodal line along the KH line. We also found that the band structure of AlB2 is
regarded as a heavily electron-doped version of MgB2 and is therefore well
suited for fully visualizing the predicted Dirac nodal line. The present
results suggest that (Al,Mg)B2 system is a promising platform for studying the
interplay among Dirac nodal line, carrier doping, and possible topological
superconducting properties.Comment: 6 pages, 3 figure
Epitaxial growth of Ca(Ge₁₋ₓSnₓ)₂ with group IV 2D layers on Si substrate
Yoshizaki T., Terada T., Uematsu Y., et al. Epitaxial growth of Ca(Ge₁₋ₓSnₓ)₂ with group IV 2D layers on Si substrate. Applied Physics Express 17, 055501 (2024); https://doi.org/10.35848/1882-0786/ad3ee2.Two-dimensional (2D) material is drawing considerable attention as a promising thermoelectric material. This study establishes the formation method of renewed Ca-intercalated group IV 2D materials, Ca(Ge₁₋ₓSnₓ)₂ crystals including germanene-based 2D layers. The solid phase epitaxy allows us to form epitaxial Ca(Ge₁₋ₓSnₓ)₂ on Si. Atomic force microscopy reveals that the Ca(Ge₁₋ₓSnₓ)₂ has island structures. X-ray diffraction proved the epitaxial growth of the Ca(Ge₁₋ₓSnₓ)₂ island structures and the increase of the c-axis lattice constant with Sn content increase. The formation of this renewed intermetallic compound including group IV 2D layer opens an avenue for high performance thermoelectric generator/Si
Ambipolar suppression of superconductivity by ionic gating in optimally-doped BaFe2(As,P)2 ultrathin films
Superconductivity (SC) in the Ba-122 family of iron-based compounds can be
controlled by aliovalent or isovalent substitutions, applied external pressure,
and strain, the combined effects of which are sometimes studied within the same
sample. Most often, the result is limited to a shift of the SC dome to
different doping values. In a few cases, the maximum SC transition at optimal
doping can also be enhanced. In this work, we study the combination of charge
doping together with isovalent P substitution and strain by performing ionic
gating experiments on BaFe(AsP) ultrathin films. We
show that the polarization of the ionic gate induces modulations to the
normal-state transport properties that can be mainly ascribed to surface charge
doping. We demonstrate that ionic gating can only shift the system away from
the optimal conditions, as the SC transition temperature is suppressed by both
electron and hole doping. We also observe a broadening of the resistive
transition, which suggests that the SC order parameter is modulated
nonhomogeneously across the film thickness, in contrast with earlier reports on
charge-doped standard BCS superconductors and cuprates.Comment: 10 pages, 5 figure
Study of hadron interactions in a lead-emulsion target
Topological and kinematical characteristics of hadron interactions have been
studied using a lead-emulsion target exposed to 2, 4 and 10 GeV/c hadron beams.
A total length of 60 m tracks was followed using a high speed automated
emulsion scanning system. A total of 318 hadron interaction vertices and their
secondary charged particle tracks were reconstructed. Measurement results of
interaction lengths, charged particle multiplicity, emission angles and momenta
of secondary charged particles are compared with a Monte Carlo simulation and
appear to be consistent. Nuclear fragments emitted from interaction vertices
were also detected by a newly developed emulsion scanning system with
wide-angle acceptance. Their emission angle distributions are in good agreement
with the simulated distributions. Probabilities of an event being associated
with at least one fragment track are found to be greater than 50% for beam
momentum GeV/c and are well reproduced by the simulation. These
experimental results validate estimation of the background due to hadron
interactions in the sample of decay candidates in the OPERA oscillation experiment.Comment: 14 pages, 11 figure
MODELING OF PAVEMENT ROUGHNESS UTILIZING ARTIFICIAL NEURAL NETWORK APPROACH FOR LAOS NATIONAL ROAD NETWORK
The International Roughness Index (IRI) has become the reference scale for assessing pavement roughness in many highway agencies worldwide. This research aims to develop two Artificial Neural Network (ANN) models for Double Bituminous Surface Treatment (DBST) and Asphalt Concrete (AC) pavement sections using Laos Pavement Management System (PMS) database for National Road Network (NRN). The final database consisted of 269 and 122 observations covering 1850 km of DBST NRN and 718 km of AC NRN, respectively. The proposed models predict IRI as a function of pavement age and Cumulative Equivalent Single-Axle Load (CESAL). The obtained data were randomly divided into training (70%), validation (15%), and testing (15%) datasets. The statistical evaluation results of the training dataset reveal that both ANN models (DBST and AC) have good prediction ability with high values of coefficient of determination (R2 = 0.96 and 0.94) and low values of Mean Absolute Error (MAE = 0.23 and 0.19) and Mean Squared Percentage Error (RMSPE = 7.03 and 9.98). Eventually, the goodness of fit of the proposed ANN models was compared with the Multiple Linear Regression (MLR) models previously developed under the same conditions. The results show that ANN models yielded higher prediction accuracy than MLR models
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