Conductance

About: Conductance is a research topic. Over the lifetime, 8088 publications have been published within this topic receiving 235961 citations.

Molecular Conductance: Chemical Trends of Anchoring Groups

Abstract: Combining density functional theory calculations for molecular electronic structure with a Green function method for electron transport, we calculate from first principles the molecular conductance of benzene connected to two Au leads through different anchoring atoms -- S, Se, and Te. The relaxed atomic structure of the contact, different lead orientations, and different adsorption sites are fully considered. We find that the molecule-lead coupling, electron transfer, and conductance all depend strongly on the adsorption site, lead orientation, and local contact atomic configuration. For flat contacts the conductance decreases as the atomic number of the anchoring atom increases, regardless of the adsorption site, lead orientation, or bias. For small bias this chemical trend is, however, dependent on the contact atomic configuration: an additional Au atom at the contact with the (111) lead changes the best anchoring atom from S to Se although for large bias the original chemical trend is recovered.

Reconciling Conductance Fluctuations and the Scaling Theory of Localization

Abstract: We reconcile the phenomenon of mesoscopic conductance fluctuations with the single parameter scaling theory of the Anderson transition. We calculate three averages of the conductance distribution, exp( ), , and 1/ , where g is the conductance in units of e(2)/h and R = 1/g is the resistance, and demonstrate that these quantities obey single parameter scaling laws. We obtain consistent estimates of the critical exponent from the scaling of all these quantities.

Generalized conductance formula for the multiband tight-binding model

Abstract: We present a generalized conductance formula for the multiband tight-binding model based on the formula by Caroli. We show that the transmission coefficients for Bloch states can be calculated using the expression for theself-energies of the leads in terms of the eigenstates of the secular matrix. We also show that evanescent states cannot be neglected in the calculation as is usually done. Although they do not explicitly contribute to the total conductance, they are needed to obtain the correct Green's function and the self-energies. This formula allows for an alternative to the usual iterative method for calculating the conductance of a molecule connected to two semi-infinite leads, and can give the contributions to the conductance decomposed by conduction channel.

The Electrical Conductivity of Solutions of Alkali Metals in their Molten Halides1

Abstract: The electrical conductivity of alkali metal solutions in their molten halides has been measured by means of a synthetic sapphire conductance cell. The specific conductance increases with increasing metal concentration. The equivalent conductance of K, A K, in both KCl and KBr also increases, namely, from 2800 ohm/sup -1/ cm/sup 2/ (K--KCl, 820 deg ), 6100 (K--KBr, 760 deg ), and 6500 (K--KBr, 870 deg ) at infinite dilution, to 38,000, 83,000, and 71,000 ohm/ sup -1/ cm/sup 2/ at 19, 23, and 20 mole% K, respectively, the maximum concentrations measured. However, LAMBDA /sub Na/, for Na in NaBr at 895 deg decreases from 12,500 to a minimum of 7300 ohm/sup -1/ cm/sup 2/ at ca. 9 mole% metal. At 805 deg /sub Na/ in NaBr decreases from ca. 12,000 at infinite dilution, i.e., approximately the same value as at 895 deg , to less than 5000, and in NaCl at both 845 and 890 deg from ca. 6000 to less than 3000 ohm/sup -1/ cm/sup 2/. These values are the equivalent conductances at 5, 4 and 3 mole% Na, respectively, representing the metal solubility limits which are too low to permit the equivalent conductance minima to be realized. Themore » different behavior of sodium and potassium may be related to the liquid phase equilibria and to the dissociation energies known for the diatomic gaseous metal molecules, both of which reflect a greater tendency to associate for Na than for K at the test temperatures. Such association, which increases with metal concentration, decreases the number of metal particles per equivalent of metal on which the electronic fraction of the conductance is thought to depend. The effect of the association, not strong enough in the K systems to produce a minimum in equivalent conductance, is, in the Na systems, surpassed, at the minimum, by the effect of the gradual establishment of the metallic conductance band through overlap of the orbitals of the metal pelymers. The differences in equivalent conductance at infinite dilution for the various systems may be taken to reflect the influence of the different degrees of polarization of the anions by the cations on electron mobility. (auth)« less

Kondo Effect in Single Quantum Dot Systems — Study with Numerical Renormalization Group Method —

Abstract: The tunneling conductance is calculated as a function of the gate voltage in wide temperature range for the single quantum dot systems with Coulomb interaction. We assume that two orbitals are active for the tunneling process. We show that the Kondo temperature for each orbital channel can be largely different. The tunneling through the Kondo resonance almost fully develops in the region \(T \lesssim 0.1 T_{\rm K}^{*} \sim 0.2 T_{\rm K}^{*}\), where T K * is the lowest Kondo temperature when the gate voltage is varied. At high temperatures the conductance changes to the usual Coulomb oscillations type. In the intermediate temperature region, the degree of the coherency of each orbital channel is different, so strange behaviors of the conductance can appear. For example, the conductance once increases and then decreases with temperature decreasing when it is suppressed at T =0 by the interference cancellation between different channels. The interaction effects in the quantum dot systems lead the sensitivit...