Resonant transport and electrostatic effects in single-molecule electrical junctions

Brooke, C. N. L.; Vezzoli, Andrea; Higgins, Simon J.; Zotti, Linda A.; Palacios, J. J.; Nichols, Richard J.

doi:10.1103/physrevb.91.195438

Cited by 31 publications

(30 citation statements)

References 57 publications

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“…Peaks in the histograms were fitted to a Gaussian distribution to determine the most probable conductance, expressed in nS. Data for the X[Ph]X class of molecular wires was taken after Brooke et al, 41 and data for the alkanedithiol series was taken from Haiss et al 29 The experimentally determined conductance values were then plotted as ln(G) vs. length, and a linear fitting was used to obtain the β′ attenuation and its standard deviation is used as error.…”

Section: Resultsmentioning

confidence: 99%

“…14,23,[35][36][37][38][39][40] They have improved our understanding of the conductance decay with length in MMM junctions, but the effect of the molecular wire structure on the value of β is still not completely understood. An important feature in the transport characteristics of alkanedithiols is the presence of a broad resonance, called in previous studies a "gateway state" 41 or "contact-level", 30 close in energy to the Fermi level of the metallic leads. In a systematic study of alkane molecular junctions with gold electrodes, Kim et al, reported a small peak close to the Fermi energy and a broad one about −1 eV from the Fermi energy, and they showed that the resonances are due to molecular orbitals localized on sulfur at these energies.…”

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confidence: 99%

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Gateway state-mediated, long-range tunnelling in molecular wires

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a If the factors controlling the decay in single-molecule electrical conductance G with molecular length L could be understood and controlled, then this would be a significant step forward in the design of highconductance molecular wires. For a wide variety of molecules conducting by phase coherent tunnelling, conductance G decays with length following the relationship G = Ae . It is widely accepted that the attenuation coefficient β is determined by the position of the Fermi energy of the electrodes relative to the energy of frontier orbitals of the molecular bridge, whereas the terminal anchor groups which bind to the molecule to the electrodes contribute to the pre-exponential factor A. We examine this premise for several series of molecules which contain a central conjugated moiety ( phenyl, viologen or α-terthiophene) connected on either side to alkane chains of varying length, with each end terminated by thiol or thiomethyl anchor groups. In contrast with this expectation, we demonstrate both experimentally and theoretically that additional electronic states located on thiol anchor groups can significantly decrease the value of β, by giving rise to resonances close to E F through coupling to the bridge moiety.This interplay between the gateway states and their coupling to a central conjugated moiety in the molecular bridges creates a new design strategy for realising higher-transmission molecular wires by taking advantage of the electrode-molecule interface properties.

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Gateway state-mediated, long-range tunnelling in molecular wires

et al. 2018

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“…This exceptional behavior is due to the evolution of the HOMO-LUMO gap that rapidly decreases with the molecular length, which compensates for the increased tunneling distance. Finally, the last example to be cited with respect to low attenuation factors is the work conducted by Brooke et al, who show a structural control on the electronic transport resonance in HS(CH 2 )n[1,4 −C 6 H 4 ](CH 2 ) n SH (n = 1, 3, 4, 6) metal-molecule-metal junctions, leading to very small attenuation factors [22]. This work offers very promising perspectives in gating the transport resonance in order to modulate the molecular junction behavior.…”

Section: Some Attenuation Factors Of Standard Molecular Junctionsmentioning

confidence: 99%

Attenuation Factors in Molecular Electronics: Some Theoretical Concepts

Dappe

2020

Applied Sciences

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Understanding the electronic transport mechanisms in molecular junctions is of paramount importance to design molecular devices and circuits. In particular, the role of the different junction components contributing to the current decay—namely the attenuation factor—is yet to be clarified. In this short review, we discuss the main theoretical approaches to tackle this question in the non-resonant tunneling regime. We illustrate our purpose through standard symmetric junctions and through recent studies on hybrid molecular junctions using graphene electrodes. In each case, we highlight the contribution from the anchoring groups, the molecular backbone and the electrodes, respectively. In this respect, we consider different anchoring groups and asymmetric junctions. In light of these results, we discuss some perspectives to describe accurately the attenuation factors in molecular electronics.

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“…A growing number of software implementations of cDFT are now appearing 1,24,26,29,30,52,[75][76][77][78][79][80] , including linear-scaling implementations designed for application to large systems 18,53 .…”

Section: Conclusion and Summarymentioning

confidence: 99%

Optimization of constrained density functional theory

O’Regan

Teobaldi

2016

Phys. Rev. B

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Constrained density functional theory (cDFT) is a versatile electronic structure method that enables ground-state calculations to be performed subject to physical constraints. It thereby broadens their applicability and utility. Automated Lagrange multiplier optimisation is necessary for multiple constraints to be applied efficiently in cDFT, for it to be used in tandem with geometry optimization, or with molecular dynamics. In order to facilitate this, we comprehensively develop the connection between cDFT energy derivatives and response functions, providing a rigorous assessment of the uniqueness and character of cDFT stationary points while accounting for electronic interactions and screening. In particular, we provide a new, non-perturbative proof that stable stationary points of linear density constraints occur only at energy maxima with respect to their Lagrange multipliers. We show that multiple solutions, hysteresis, and energy discontinuities may occur in cDFT. Expressions are derived, in terms of convenient by-products of cDFT optimization, for quantities such as the dielectric function and a condition number quantifying ill-definition in multi-constraint cDFT.Comment: 15 pages, 6 figure

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Resonant transport and electrostatic effects in single-molecule electrical junctions

Cited by 31 publications

References 57 publications

Gateway state-mediated, long-range tunnelling in molecular wires

Gateway state-mediated, long-range tunnelling in molecular wires

Attenuation Factors in Molecular Electronics: Some Theoretical Concepts

Optimization of constrained density functional theory

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