97 research outputs found
TWO MORE SOCIAL WASP SPECIES (VESPIDAE, POLISTINAE) COLLECT MULLERIAN BODIES FROM CECROPIA TREES (URTICACEAE)
The interactive behaviors of two species of social wasps, Protopolybia chartergoides (Gribodo) and Charterginus fulvus Fox with Cecropia obtusifolia (Cecropiaceae) are described. The use of Cecropia Müllerian bodies by the two wasps is also described, as well as the distribution of this trait in Protopolybia and Charterginus
On-Surface Synthesis of Silole and Disilacyclooctaene Derivatives
Sila-cyclic rings are a class of organosilicon cyclic compounds and have
abundant application in organic chemistry and materials science. However, it is
still challenging to synthesize compounds with sila-cyclic rings in solution
chemistry due to their low solubility and high reactivity. Recently, on-surface
synthesis was introduced into organosilicon chemistry as 1,4- disilabenzene
bridged nanostructures were obtained via coupling between bromo-substituted
molecules and silicon atoms on Au(111). Here, we extend this strategy for
syntheses of silole derivatives and graphene nanoribbons with eight-membered
sila-cyclic rings from 2,2',6,6'- tetrabromobiphenyl and
1,4,5,8-tetrabromonaphthalene on Au(111), respectively. Their structures and
electronic properties were investigated by a combination of scanning tunneling
microscopy/spectroscopy and density functional theory calculations. This work
demonstrates a generality of this synthesis strategy to fabricate various
silicon incorporated nanostructures
Local Probe Isomerization in a One-Dimensional Molecular Array
Synthesis of one-dimensional molecular arrays with tailored stereoisomers is
challenging yet has a great potential for application in molecular opto-,
electronic- and magnetic-devices, where the local array structure plays a
decisive role in the functional properties. Here, we demonstrate construction
and characterization of dehydroazulene isomer and diradical units in
three-dimensional organometallic compounds on Ag(111) with a combination of
low-temperature scanning tunneling microscopy and density functional theory
calculations. Tip-induced voltage pulses firstly result in the formation of a
diradical species via successive homolytic fission of two C-Br bonds in the
naphthyl groups, which are subsequently transformed into chiral dehydroazulene
moieties. The delicate balance of the reaction rates among the diradical and
two stereoisomers, arising from an in-line configuration of tip and molecular
unit, allows directional azulene-to-azulene and azulene-to-diradical local
probe isomerization in a controlled manner. Furthermore, we found that the
diradical moiety hosts an open-shell singlet with antiferromagnetic coupling
between the unpaired electrons, which can undergo an inelastic spin transition
of 91 meV to the ferromagnetically coupled triplet state
Electronic and magnetic characterization of epitaxial CrBr monolayers
The ability to imprint a given material property to another through proximity
effect in layered two-dimensional materials has opened the way to the creation
of designer materials. Here, we use molecular-beam epitaxy (MBE) for a direct
synthesis of a superconductor-magnet hybrid heterostructure by combining
superconducting niobium diselenide (NbSe) with the monolayer ferromagnetic
chromium tribromide (CrBr). Using different characterization techniques and
density-functional theory (DFT) calculations, we have confirmed that the
CrBr monolayer retains its ferromagnetic ordering with a magnetocrystalline
anisotropy favoring an out-of-plane spin orientation. Low-temperature scanning
tunneling microscopy (STM) measurements show a slight reduction of the
superconducting gap of NbSe and the formation of a vortex lattice on the
CrBr layer in experiments under an external magnetic field. Our results
contribute to the broader framework of exploiting proximity effects to realize
novel phenomena in 2D heterostructures
Emergence of Exotic Spin Texture in Supramolecular Metal Complexes on a 2D Superconductor
Designer heterostructures, where the desired physics emerges from the
controlled interactions between different components, represent one of the most
powerful strategies to realize unconventional electronic states. This approach
has been particularly fruitful in combining magnetism and superconductivity to
create exotic superconducting states. In this work, we use a heterostructure
platform combining supramolecular metal complexes (SMCs) with a quasi-2D van
der Waals (vdW) superconductor NbSe. Our scanning tunneling microscopy
(STM) measurements demonstrate the emergence of Yu-Shiba-Rusinov (YSR) bands
arising from the interaction between the SMC magnetism and the NbSe
superconductivity. Using X-ray absorption spectroscopy (XAS) and X-ray magnetic
circular dichroism (XMCD) measurements, we show the presence of
antiferromagnetic coupling between the SMC units. These result in the emergence
of an unconventional reconstruction in the magnetic ground state
that is directly reflected in real space modulation of the YSR bands. The
combination of flexible molecular building blocks, frustrated magnetic
textures, and superconductivity in heterostructures establishes a fertile
starting point to fabricating tunable quantum materials, including
unconventional superconductors and quantum spin liquids
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