Conductance and activation energy for electron transport in series and parallel intramolecular circuits

Abstract

We investigate electron transport through series and parallel intramolecular circuits in the framework of the multi-level Redfield theory. Based on the assumption of weak monomer-bath couplings, the simulations depict the length and temperature dependence in six types of intramolecular circuits. In the tunneling regime, we find that the intramolecular circuit rule is only valid in the weak monomer coupling limit. In the thermally activated hopping regime, for circuits based on two different molecular units M and M with distinct activation energies E > E, the activation energies of M and M in series are nearly the same as E while those in parallel are nearly the same as E. This study gives a comprehensive description of electron transport through intramolecular circuits from tunneling to thermally activated hopping. We hope that this work can motivate additional studies to design intramolecular circuits based on different types of building blocks, and to explore the corresponding circuit laws and the length and temperature dependence of conductance.

Directional Excitation of Surface Plasmon Polaritons via Molecular Through-Bond Tunneling across Double-Barrier Tunnel Junctions

“…Molecular tunneling junctions have been used, for example, to tune the tunneling charge transfer plasmon mode − and to excite , or detect SPPs. , In principle, the shape of the tunneling barrier of molecular junctions can be readily changed. For example, molecules with a conductive conjugated and relatively insulating aliphatic part should result in molecular double-barrier junctions, − but it has not been experimentally verified whether the charge carriers probe two distinct barriers or an average barrier because in two-terminal junctions only the total currents across the junctions can be measured and interpretation of data therefore relies on theoretical models with associated simplifications and assumptions.…”

“…Equation , however, fails to capture the shape of the tunneling barrier. It has been suggested that molecular junctions can be seen as “series tunneling junctions” where each molecular component forms a distinct part of the tunnel junction. − According to this view of molecular junctions, here, the alkyl chain and BPh units pose two distinct tunneling barriers in series where the tunneling barrier widths are defined by the lengths of the alkyl chain (which depends on n ), d alk , and the BPh unit, d BPh , and tunneling barrier heights are defined by the alkyl chain, φ alk , and BPh unit, φ BPh (Figure c). Thus, in principle, the junctions are double-barrier junctions with the corresponding tunneling decay coefficients along the alkyl chain, β alk , and BPh units, β BPh , given by eq In general, the aromatic part poses a lower φ than the aliphatic molecules (as indicated in Figure c); consequently, aromatic molecules have typical values of β in the range of 0.2–0.4 Å –1 , − whereas aliphatic molecules have β of 0.8 Å –1 .…”

Polygonal current models for polycyclic aromatic hydrocarbons and graphene sheets of various shapes

“…n kgraph has been evaluated, via linear regression, from the slope of a straight line, eqs. (8) and (11). r CM k is the p-electron contribution to the out-of-plane component of the magnetic shielding at the center of mass from eq.…”

“…[29,30,33,49] A more general definition of current susceptibility vector has been proposed. [65] The relationships (1), (8), and (10) hold in the limit of the one-loop polygonal model based on classical BSL. [46,47] They are not supposed to work with satisfactory accuracy for PAHs supporting delocalized currents flowing in many loops, which may have different centers and areas and are placed at different heights from the plane of the molecule.…”

“…In fact, graphene can conduct electricity more effectively than copper, which implicates great potential and prospects for countless technological applications. Peculiar aspects of conductivity [7][8][9] and special mobility, [10][11][12][13] magnetotransport, and quantum Hall effect [1] have been investigated.…”