A direct calculation of the tunnelling current. II. Free electron description

Caroli, C.; Combescot, R.; Lederer, Dieter; Nozières, P.; Saint‐James, D.

doi:10.1088/0022-3719/4/16/025

Cited by 174 publications

(132 citation statements)

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“…It combines the non-equilibrium Green's function (NEGF) formalism 23 with density functional theory which is implemented in the SIESTA code 24 . We use the Perdew-Burke-Ernzerhof 25 exchange-correlation functional and 400 Ry energy cutoff to define real-space grid for the density manipulation.…”

Section: Technical Detailsmentioning

confidence: 99%

Ferrocene-1,1′-dithiol as molecular wire between Ag electrodes: The role of surface defects

Bredow

Tegenkamp

Pfnür

et al. 2008

The Journal of Chemical Physics

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The interaction of ferrocene-1,1 ′ -dithiol (FDT) with two parallel Ag(111) surfaces has been theoretically studied at density-functional level. The effect of surface defects on the energetic and electronic structure was investigated. The electronic transport properties are studied with the non-equilibrium Green's function approach. The adsorption geometry has a strong effect on the electronic levels and conductivity. The presence of point defects strongly enhances the molecule-surface interaction but has a surprisingly small effect on the density of states near the Fermi energy. The FDT-surface bond is particularly strong near terraces or steps and leads to significant shifts of the molecular orbitals relative to the gas phase. For all considered defect types except the single adatom the electronic conductivity through the FDT molecule is decreased compared to adsorption on perfect surfaces.PACS 71.15.Mb, 73.63.Kv 2

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Section: Technical Detailsmentioning

confidence: 99%

Ferrocene-1,1′-dithiol as molecular wire between Ag electrodes: The role of surface defects

Bredow

Tegenkamp

Pfnür

et al. 2008

The Journal of Chemical Physics

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“…Most theoretical works on quantum transport focus on steady-state properties and are based on a "contacting approach" first introduced by Caroli et al 1,2,3,4 In this approach the system is separated in isolated parts in the remote past (left/right leads and central device) and the contacts between subsystems are treated as a time-dependent perturbation (adiabatic switching). Such a partition is crucial in the formal derivation of the Meir-Wingreen formula, 5 which allows for studying timedependent phenomena and correlation effects in the device region but is not suitable to include long-range interactions and memory effects in a first-principle manner (see discussion below).…”

Section: Introductionmentioning

confidence: 99%

Bound states inab initioapproaches to quantum transport: A time-dependent formulation

Stefanucci

2007

Phys. Rev. B

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In this work we study the role of bound electrons in quantum transport. The partition-free approach by Cini is combined with time-dependent density functional theory (TDDFT) to calculate total currents and densities in interacting systems. We show that the biased electrode-deviceelectrode system with bound states does not evolve towards a steady regime. The density oscillates with history-dependent amplitudes and, as a consequence, the effective potential of TDDFT oscillates too. Such time dependence might open new conductive channels, an effect which is not accounted for in any steady-state approach and might deserve further investigations.

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“…SMEAGOL combines the non-equilibrium Green's function (NEGF) formalism 2,14,15,16,17,18 with density functional theory (DFT) 19 , using the numerical implementation contained in the SIESTA code 20,21 . The system (molecule plus leads) is ideally divided in three regions: namely a left and a right lead, and a scattering region comprising the H 2 molecule and part of the leads themselves 22 .…”

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confidence: 99%

Single-channel conductance ofH2molecules attached to platinum or palladium electrodes

et al. 2005

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We report a detailed theoretical study of the bonding and conduction properties of an Hydrogen molecule joining either platinum or palladium electrodes. We show that an atomic arrangement where the molecule is placed perpendicular to the electrodes is unstable for all distances between electrodes. In contrast, the configuration where the molecule bridges the electrodes is stable in a wide range of distances. In this last case the bonding state of the molecule does not hybridize with the leads and remains localized within the junction. As a result, this state does not transmit charge so that electronic transport is carried only through the anti-bonding state. This fact leads to conductances of 1 G0 at most, where G0 = 2e 2 /h. We indeed find that G is equal to 0.9 and 0.6 G0 for Pt and Pd contacts respectively. PACS numbers: 73.63.Rt, 71.15.Mb The main obstacle to using single molecules as conducting elements 1 is the difficulty in establishing stable and reproducible contacts to metallic electrodes. Conductance quantization in atomic constrictions was predicted several years ago 2 , but the practical realization in single-molecule contacts only became possible in the mid-90's, with the advent of the scanning tunneling microscope 3,4,5 and mechanically controllable break junctions6 .An important testing ground for both theory and experiment is the simplest of all molecular bridges, namely the H 2 molecule. This molecule has just one bonding and one anti-bonding state in the available energy range. Therefore it should be possible to predict the effect of tuning a range of adjustable parameters, including the position and orientation of the molecule, the distance and voltage between the electrodes and the materials that make up the electrodes. Despite the apparent simplicity of this junction, there is currently no agreement about what are the position and orientation of the molecule for given separation between the electrodes, even for zero applied bias.Smit and coworkers 7 found that the conductance histograms of the molecule, sandwiched between Pt leads, had a sharp peak at about 0.9 G 0 (G 0 = 2e 2 /h is the conductance quantum) and therefore argued that electronic transport was dominated by a single channel with an almost perfect transmission. In addition, from the experimental phonon spectra they concluded that the molecule bonds to the electrodes in a bridge configuration (BC), i.e. with the H 2 bond axis parallel to the transport direction (see Fig.1(a)). This was also confirmed by Cuevas et al. 8 .A different interpretation was given by García and coworkers 9 who showed theoretically that an arrangement where the molecule bonds perpendicularly to the transport direction (perpendicular configuration, PC) has a lower energy, and therefore should also be the preferred atomic configuration * Present address: Department of Physics, Lancaster University, Lancaster, LA1 4YB, U. K.(see Fig. 1(b)). Their simulations gave conductances of order 1 G 0 and 0.2 G 0 for PC and BC, respectively. Very recently, Thygesen ...

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A direct calculation of the tunnelling current. II. Free electron description

Cited by 174 publications

References 1 publication

Ferrocene-1,1′-dithiol as molecular wire between Ag electrodes: The role of surface defects

Ferrocene-1,1′-dithiol as molecular wire between Ag electrodes: The role of surface defects

Bound states inab initioapproaches to quantum transport: A time-dependent formulation

Single-channel conductance ofH2molecules attached to platinum or palladium electrodes

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