4,338 research outputs found
Spatially Inhomogeneous Superconducting State near in UPdAl
We have performed Al-NMR measurements on single-crystalline
UPdAl with the field parallel to the axis to investigate the
superconducting (SC) properties near the upper critical field of
superconductivity . The broadening of the NMR linewidth below 14~K
indicates the appearance of the internal field at the Al site, which originates
from the antiferromagnetically ordered moments of U 5 electrons. In the SC
state well below = 3.4~T, the broadening of the NMR linewidth
due to the SC diamagnetism and a decrease in the Knight shift are observed,
which are well-understood by the framework of spin-singlet superconductivity.
In contrast, the Knight shift does not change below , and the NMR
spectrum is broadened symmetrically in the SC state in the field range of 3~T
. The unusual NMR spectrum near
suggests that a spatially inhomogeneous SC state such as the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state would be realized.Comment: 5 pages, 5 figure
Borylstannylation of alkynes with inverse regioselectivity: copper-catalyzed three-component coupling using a masked diboron
A variety of terminal alkynes are facilely convertible into cis-boryl(stannyl)alkenes with inverse regioselectivity to those of the previous borylstannylation by the copper-catalyzed three-component reaction using a masked diboron. The synthetic utility of the resulting boryl(stannyl)alkenes has been demonstrated by chemoselective coupling reactions
Copper-catalyzed α-selective hydrostannylation of alkynes for the synthesis of branched alkenylstannanes
A variety of branched alkenylstannanes can directly be synthesized with excellent α-selectivity by the copper-catalyzed hydrostannylation using a distannane or a silylstannane, irrespective of the electronic and steric characteristics of terminal alkynes employed. Synthetic utility of the resulting branched alkenylstannane has been demonstrated by the total synthesis of bexarotene
Inverse regioselectivity in the silylstannylation of alkynes and allenes: copper-catalyzed three-component coupling with a silylborane and a tin alkoxide
Silylstannylation of alkynes and allenes has been found to proceed by three-component coupling using a silylborane and a tin alkoxide in the presence of a Cu(I) catalyst. The regioselectivities are completely inverse to those of the conventional silylstannylation under palladium catalysis
Numerical investigations of mechanical stress caused in dendrite by melt convection and gravity
In order to investigate the effects of stress around dendrite neck cased by the convection and gravity on the dendrite fragmentation, the novel numerical model, where phase-field method, Navier-Stokes equations and finite element method are continuously and independently employed, has been developed. By applying the model to the dendritic solidification of Al-Si alloy, the maximum stress variations by melt convection and gravity with dendrite growth were evaluated
Spatial Current Patterns, Dephasing and Current Imaging in Graphene Nanoribbons
Using the non-equilibrium Keldysh Green's function formalism, we investigate
the local, non-equilibrium charge transport in graphene nanoribbons (GNRs). In
particular, we demonstrate that the spatial current patterns associated with
discrete transmission resonances sensitively depend on the GNRs' geometry,
size, and aspect ratio, the location and number of leads, and the presence of
dephasing. We identify a relation between the spatial form of the current
patterns, and the number of degenerate energy states participating in the
charge transport. Furthermore, we demonstrate a principle of superposition for
the conductance and spatial current patterns in multiple-lead configurations.
We demonstrate that scanning tunneling microscopy (STM) can be employed to
image spatial current paths in GNR with atomic resolution, providing important
insight into the form of local charge transport. Finally, we investigate the
effects of dephasing on the spatial current patterns, and show that with
decreasing dephasing time, the current patterns evolve smoothly from those of a
ballistic quantum network to those of classical resistor network.Comment: 25 pages, 12 figure
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