Topic
Conductance
About: Conductance is a research topic. Over the lifetime, 8088 publications have been published within this topic receiving 235961 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: Analysis of the voltage and concentration dependence of macroscopic conductances induced by Zrv-IIB suggests that, on average, channels contain ca.
Abstract: The zervamicins (Zrv) are a family of 16 residue peptaibol channel formers, related to the 20 residue peptaibol alamethicin (Alm), but containing a higher proportion of polar sidechains. Zrv-IIB forms multi-level channels in planar lipid (diphytanoyl phosphatidyl- choline) bilayers in response to cis positive voltages. Analysis of the voltage and concentration dependence of macroscopic conductances induced by Zrv-IIB suggests that, on average, channels contain ca. 13 peptide monomers. Analysis of single channel conductance levels suggests a similar value. The pattern of successive conductance levels is consistent with a modified helix bundle model in which the higher order bundle are distorted within the plane of the bilayer towards a "torpedo" shaped cross-section, The kinetics of intra-burst switching between adjacent conductance levels are shown to be approximately an order of magnitude faster for Zrv-IIB than for Ahn. The channel forming properties of the related naturally occurring peptaibols, Zrv-Leu and Zrv-IC, have also been demonstrated, as have those of the synthetic apolar analogue Zrv-Al-16. The experimental studies on channel formation are combined with the known crystallographic structures of Zrv-Al-16 and Zrv- Leu to develop a molecular model of Zrv-IIB channels.
62 citations
TL;DR: It is demonstrated that photoconductance at resonant illumination arises due to the Coulomb interaction between the electrons and holes in the molecular bridge, so-called exciton-binding.
Abstract: We report on a theoretical analysis and experimental verification of a mechanism for photoconductance, the change in conductance upon illumination, in symmetric single-molecule junctions. We demonstrate that photoconductance at resonant illumination arises due to the Coulomb interaction between the electrons and holes in the molecular bridge, so-called exciton-binding. Using a scanning tunneling microscopy break junction technique, we measure the conductance histograms of perylene tetracarboxylic diimide (PTCDI) molecules attached to Au-electrodes, in the dark and under illumination, and show a significant and reversible change in conductance, as expected from the theory. Finally, we show how our description of the photoconductance leads to a simple design principle for enhancing the performance of molecular switches.
62 citations
15 Aug 2011
TL;DR: A polarization that is able to explain the complex conductivity spectra including the grain size distribution, the porosity, and the complexation of the mineral surface with the ions of the pore water is presented.
Abstract: Low-frequency dielectric spectroscopy can be measured in terms of a conductance and a phase lag between the electrical current and the electrical field. This conductance and phase lag can be written as into a complex conductivity with both an in-phase and quadrature components that are frequency dependent. In sands, the low-frequency (10 mHz-40 kHz) spectra of the complex conductivity are dominated by the polarization of the electrical double layer (especially the internal part of the electrical double layer called the Stern layer) and the Maxwell-Wagner polarization (typically above 100 Hz). We present a polarization that is able to explain the complex conductivity spectra including the grain size distribution, the porosity, and the complexation of the mineral surface with the ions of the pore water. To test this model, we investigate the sorption of various cations (Na, Pb, Zn) characterized by different affinities with the surface of silica. Sand column experiments were carried out to see the change in the complex conductivity during the advective/dispersive transport of a lead nitrate solution and a zinc sulfate solution, replacing a sodium chloride solution in the pore space of the sand. The complex conductivity model is able to explain the change of the phase over time.
62 citations
TL;DR: In this article, anomalous spikes were observed in differential conductance measurements on various single-molecule contacts, which can be used as a new spectroscopic tool for identifying molecular vibration modes.
Abstract: A single atom or molecule with an almost transparent single conductance channel leading to a conductance near the conductance quantum 2e 2 =h�� 1G0� can be contacted to leads. Conduction electrons can pass through such junction ballistically for low bias voltages since the mean free path of the electrons is much larger than the size of the contact. However, the contact is not entirely ballistic in the sense that once the excess energy of the conduction electrons becomes equal to or larger than the energy of a local mode of the contact, the electrons can scatter inelastically by exciting a local mode. This results in the case of a perfectly transmitting single channel contact to a small decrease in the conductance, since the forward traveling electrons are backscattered due to the energy loss in the inelastic scattering process. Differential conductance (dI=dV) measurements have identified vibration modes of single molecules in an atomic contact [1]. This technique, also called point contact spectroscopy is analogous to inelastic electron tunneling spectroscopy (IETS) for single molecules [2,3], with the difference that the conductance in the latter case increases due to the opening of an additional conductance channel. In this Letter we present the observation of anomalous spikes, rather than steps, in dI=dV measurements on various single-molecule contacts. We present a model that involves two-level systems, which describes our data very well. It may be used as a new spectroscopic tool for identifying molecular vibration modes in single-molecule junctions.
62 citations
TL;DR: The electron transport through a graphene nanoribbon-superconductor junction is studied using the tight-binding model and the non-equilibrium Green's function method and the finite bias case, in which the Andreev reflection coefficient and normal tunneling coefficient are studied.
Abstract: We study the electron transport through a graphene nanoribbon-superconductor junction. Both zigzag and armchair edge graphene nanoribbons are considered, and the effects of the magnetic field and disorder on the transport property are investigated. By using the tight-binding model and the non-equilibrium Green's function method, the expressions of the current, conductance, normal tunneling coefficient, and Andreev reflection coefficient are obtained. For a clean system and at zero magnetic field, the linear conductance increases approximatively in a linear fashion with the on-site energy. In the presence of a magnetic field and a moderate disorder, the linear conductance exhibits plateau structures for both armchair and zigzag edges. The plateau values increase with the width of the graphene ribbon. With a wide sample width, a saturated plateau value of $|
u|e^2/h$ emerges at the filling factor $
u$. For a small filling factor, the conductance can reach the saturated value at a small width, but for a high filling factor, it requires to have a quite wide sample width to reach the saturated value. In particular, the Andreev reflection coefficient is always at 0.5 after reaching the saturated value, independent of any system parameters. In addition, we also consider the finite bias case, in which the Andreev reflection coefficient and normal tunneling coefficient are studied.
62 citations