436 research outputs found
1095-199 Disparity between dobutamine stress and physical exercise magnetic resonance imaging in patients with an intra-atrial correction for transposition of the great arteries
Orbital Interaction Mechanisms of Conductance Enhancement and Rectification by Dithiocarboxylate Anchoring Group
We study computationally the electron transport properties of
dithiocarboxylate terminated molecular junctions. Transport properties are
computed self-consistently within density functional theory and nonequilibrium
Green's functions formalism. A microscopic origin of the experimentally
observed current amplification by dithiocarboxylate anchoring groups is
established. For the 4,4'-biphenyl bis(dithiocarboxylate) junction, we find
that the interaction of the lowest unoccupied molecular orbital (LUMO) of the
dithiocarboxylate anchoring group with LUMO and highest occupied molecular
orbital (HOMO) of the biphenyl part results in bonding and antibonding
resonances in the transmission spectrum in the vicinity of the electrode Fermi
energy. A new microscopic mechanism of rectification is predicted based on the
electronic structure of asymmetrical anchoring groups. We show that the peaks
in the transmission spectra of 4'-thiolato-biphenyl-4-dithiocarboxylate
junction respond differently to the applied voltage. Depending upon the origin
of a transmission resonance in the orbital interaction picture, its energy can
be shifted along with the chemical potential of the electrode to which the
molecule is more strongly or more weakly coupled
Strong and broadly tunable plasmon resonances in thick films of aligned carbon nanotubes
Low-dimensional plasmonic materials can function as high quality terahertz
and infrared antennas at deep subwavelength scales. Despite these antennas'
strong coupling to electromagnetic fields, there is a pressing need to further
strengthen their absorption. We address this problem by fabricating thick films
of aligned, uniformly sized carbon nanotubes and showing that their plasmon
resonances are strong, narrow, and broadly tunable. With thicknesses ranging
from 25 to 250 nm, our films exhibit peak attenuation reaching 70%, quality
factors reaching 9, and electrostatically tunable peak frequencies by a factor
of 2.3x. Excellent nanotube alignment leads to the attenuation being 99%
linearly polarized along the nanotube axis. Increasing the film thickness
blueshifts the plasmon resonators down to peak wavelengths as low as 1.4
micrometers, promoting them to a new near-infrared regime in which they can
both overlap the S11 nanotube exciton energy and access the technologically
important infrared telecom band.Comment: 19 pages, 5 figures, main text followed by supporting informatio
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