770 research outputs found
Modeling transport through single-molecule junctions
Non-equilibrium Green's functions (NEGF) formalism combined with extended
Huckel (EHT) and charging model are used to study electrical conduction through
single-molecule junctions. Analyzed molecular complex is composed of asymmetric
1,4-Bis((2'-para-mercaptophenyl)-ethinyl)-2-acetyl-amino-5-nitro-benzene
molecule symmetrically coupled to two gold electrodes [Reichert et al., Phys.
Rev. Lett. Vol.88 (2002), pp. 176804]. Owing to this model, the accurate values
of the current flowing through such junction can be obtained by utilizing basic
fundamentals and coherently deriving model parameters. Furthermore, the
influence of the charging effect on the transport characteristics is
emphasized. In particular, charging-induced reduction of conductance gap,
charging-induced rectification effect and charging-generated negative value of
the second derivative of the current with respect to voltage are observed and
examined for molecular complex.Comment: 8 pages, 3 figure
Towards unified understanding of conductance of stretched monatomic contacts
When monatomic contacts are stretched, their conductance behaves in
qualitatively different ways depending on their constituent atomic elements.
Under a single assumption of resonance formation, we show that various
conductance behavior can be understood in a unified way in terms of the
response of the resonance to stretching. This analysis clarifies the crucial
roles played by the number of valence electrons, charge neutrality, and orbital
shapes.Comment: 2 figure
Quantum transport through STM-lifted single PTCDA molecules
Using a scanning tunneling microscope we have measured the quantum
conductance through a PTCDA molecule for different configurations of the
tip-molecule-surface junction. A peculiar conductance resonance arises at the
Fermi level for certain tip to surface distances. We have relaxed the molecular
junction coordinates and calculated transport by means of the Landauer/Keldysh
approach. The zero bias transmission calculated for fixed tip positions in
lateral dimensions but different tip substrate distances show a clear shift and
sharpening of the molecular chemisorption level on increasing the STM-surface
distance, in agreement with experiment.Comment: accepted for publication in Applied Physics
Dielectric constant obtained from TDR and volumetric moisture of soils in southern Brazil
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