Tunneling and Resonant Conductance in One-Dimensional Molecular Structures

TL;DR

This paper develops a Green's function-based theory for electron tunneling and resonant conductance in one-dimensional molecular structures, emphasizing the role of many-electron effects and bound states in transport mechanisms.

Contribution

It introduces a sub-barrier scattering formalism to predict tunneling amplitudes and interpret conductance via bound electron states, including effects of applied electric fields.

Findings

Resonant tunneling via bound states dominates electron transport in long organic molecules.

The method predicts I-V characteristics under finite bias conditions.

The theory explains experimental phenomena like tunneling bridge effects and conductance thresholds.

Abstract

We present a theory of tunneling and resonant transitions in one-dimensional molecular systems which is based on Green's function theory of electron sub-barrier scattering off the structural units (or functional groups) of a molecular chain. We show that the many-electron effects are of paramount importance in electron transport and they are effectively treated using a formalism of sub-barrier scattering operators. The method which calculates the total scattering amplitude of the bridge molecule not only predicts the enhancement of the amplitude of tunneling transitions in course of tunneling electron transfer through one-dimensional molecular structures but also allows us to interpret conductance mechanisms by calculating the bound energy spectrum of the tunneling electron, the energies being obtained as poles of the total scattering amplitude of the bridge molecule. We found that the resonant tunneling via bound states of the tunneling electron is the major mechanism of electron conductivity in relatively long organic molecules. The sub-barrier scattering technique naturally includes a description of tunneling in applied electric fields which allows us to calculate I-V curves at finite bias. The developed theory is applied to explain experimental findings such as bridge effect due to tunneling through organic molecules, and threshold versus Ohmic behavior of the conductance due to resonant electron transfer.