191 research outputs found
The kagom\'e metals RbTiBi and CsTiBi
The kagom\'e metals RbTiBi and CsTiBi were synthesized both
as polycrystalline powders by heating the elements an argon atmosphere and as
single crystals grown using a self-flux method. The compounds crystallize in
the hexagonal crystal system isotypically to KVSb (P6/mmm, Z = 1,
CsTi3Bi5: a = 5.7873(1) {\AA}, c = 9.2062(1) {\AA}; RbTi3Bi5: a = 5.773(1)
{\AA}, c = 9.065(1) {\AA}). Titanium atoms form a kagom\'e net with bismuth
atoms in the hexagons as well as above and below the triangles. The alkali
metal atoms are coordinated by 12 bismuth atoms and form AlB-like slabs
between the kagom\'e layers. Magnetic susceptibility measurements with
CsTiBi and RbTiBi single crystals reveal Pauli-paramagnetism
and traces of superconductivity caused by CsBi/RbBi impurities.
Magnetotransport measurements reveal conventional Fermi liquid behavior and
quantum oscillations indicative of a single dominant orbit at low temperature.
DFT calculations show the characteristic metallic kagom\'e band structure
similar to that of CsVSb with reduced band filling. A symmetry analysis
of the band structure does not reveal an obvious and unique signature of a
nontrivial topology.Comment: 20 pages, 5 Figures, submitte
The MUSE-Wide Survey: Survey Description and First Data Release
We present the MUSE-Wide survey, a blind, 3D spectroscopic survey in the
CANDELS/GOODS-S and CANDELS/COSMOS regions. Each MUSE-Wide pointing has a depth
of 1 hour and hence targets more extreme and more luminous objects over 10
times the area of the MUSE-Deep fields (Bacon et al. 2017). The legacy value of
MUSE-Wide lies in providing "spectroscopy of everything" without photometric
pre-selection. We describe the data reduction, post-processing and PSF
characterization of the first 44 CANDELS/GOODS-S MUSE-Wide pointings released
with this publication. Using a 3D matched filtering approach we detected 1,602
emission line sources, including 479 Lyman- (Lya) emitting galaxies
with redshifts . We cross-match the emission line
sources to existing photometric catalogs, finding almost complete agreement in
redshifts and stellar masses for our low redshift (z < 1.5) emitters. At high
redshift, we only find ~55% matches to photometric catalogs. We encounter a
higher outlier rate and a systematic offset of z0.2 when
comparing our MUSE redshifts with photometric redshifts. Cross-matching the
emission line sources with X-ray catalogs from the Chandra Deep Field South, we
find 127 matches, including 10 objects with no prior spectroscopic
identification. Stacking X-ray images centered on our Lya emitters yielded no
signal; the Lya population is not dominated by even low luminosity AGN. A total
of 9,205 photometrically selected objects from the CANDELS survey lie in the
MUSE-Wide footprint, which we provide optimally extracted 1D spectra of. We are
able to determine the spectroscopic redshift of 98% of 772 photometrically
selected galaxies brighter than 24th F775W magnitude. All the data in the first
data release - datacubes, catalogs, extracted spectra, maps - are available on
the website https://musewide.aip.de. [abridged]Comment: 25 pages 15+1 figures. Accepted, A&A. Comments welcom
Electronic nematicity without charge density waves in titanium-based kagome metal
Layered crystalline materials that consist of transition metal atoms on a
kagome network have emerged as a versatile platform to study unusual electronic
phenomena. For example, in the vanadium-based kagome superconductors AV3Sb5
(where A can stand for K, Cs, or Rb) there is a parent charge density wave
phase that appears to simultaneously break both the translational and the
rotational symmetry of the lattice. Here, we show a contrasting situation where
electronic nematic order - the breaking of rotational symmetry without the
breaking of translational symmetry - can occur without a corresponding charge
density wave. We use spectroscopic-imaging scanning tunneling microscopy to
study the kagome metal CsTi3Bi5 that is isostructural to AV3Sb5 but with a
titanium atom kagome network. CsTi3Bi5 does not exhibit any detectable charge
density wave state, but comparison to density functional theory calculations
reveals substantial electronic correlation effects at low energies. Comparing
the amplitudes of scattering wave vectors along different directions, we
discover an electronic anisotropy that breaks the six-fold symmetry of the
lattice, arising from both in-plane and out-of-plane titanium-derived d
orbitals. Our work uncovers the role of electronic orbitals in CsTi3Bi5,
suggestive of a hexagonal analogue of the nematic bond order in Fe-based
superconductors.Comment: This is the submitted version. Final manuscript will appear in Nature
Physic
A multi-model case study on aerosol feedbacks in online coupled chemistry-meteorology models within the COST action ES1004 EuMetChem
A multi-model case study on aerosol-meteorology interactions with regional online coupled chemistry-meteorology models
Regional effects of atmospheric aerosols on temperature: An evaluation of an ensemble of online coupled models
The climate effect of atmospheric aerosols is associated with their
influence on the radiative budget of the Earth due to the direct
aerosol–radiation interactions (ARIs) and indirect effects, resulting from
aerosol–cloud–radiation interactions (ACIs). Online coupled
meteorology–chemistry models permit the description of these effects on the
basis of simulated atmospheric aerosol concentrations, although there is
still some uncertainty associated with the use of these models. Thus,
the objective of this work is to assess whether the inclusion of atmospheric
aerosol radiative feedbacks of an ensemble of online coupled models improves
the simulation results for maximum, mean and minimum temperature at 2 m over
Europe. The evaluated models outputs originate from EuMetChem COST Action
ES1004 simulations for Europe, differing in the inclusion (or omission) of
ARI and ACI in the various models. The cases studies cover two important
atmospheric aerosol episodes over Europe in the year 2010: (i) a heat wave event
and a forest fire episode (July–August 2010) and (ii) a more humid episode
including a Saharan desert dust outbreak in October 2010. The simulation
results are evaluated against observational data from the E-OBS gridded database.
The results indicate that, although there is only a slight improvement in the
bias of the simulation results when including the radiative feedbacks, the
spatiotemporal variability and correlation coefficients are improved for the
cases under study when atmospheric aerosol radiative effects are included
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