Quantum Transport through Organic Molecules

TL;DR

This paper investigates electron transport in benzene-based molecular junctions using a tight-binding model and Green's function formalism, revealing how geometry, coupling, and magnetic fields influence conductance and current behavior.

Contribution

It introduces an analytic tight-binding approach to model quantum transport in molecular systems, highlighting effects of geometry, coupling strength, and magnetic flux.

Findings

Conductance shows resonant peaks at molecular energy levels.

Current exhibits staircase behavior in weak coupling and continuous variation in strong coupling.

Magnetic flux causes oscillatory conductance with flux-quantum periodicity.

Abstract

We explore electron transport properties for the model of benzene-1, 4-dithiolate (BDT) molecule and for some other geometric models of benzene molecule attached to two semi-infinite one-dimensional metallic electrodes using the Green's function formalism. An analytic approach, based on a simple tight-binding framework, is presented to describe electron transport through the molecular wires. Electronic transport in such molecular systems is strongly affected by the geometry of the molecules as well as their coupling to the side-attached electrodes. Conductance reveals resonant peaks associated with the molecular energy eigenstates providing several complex spectra. Current passing through the molecules shows staircase-like behavior with sharp steps in the weak molecule-to-electrode coupling limit, while it varies quite continuously with the applied bias voltage in the limit of strong molecular coupling. In the presence of transverse magnetic field, conductance exhibits oscillatory behavior with flux $\phi$, threaded by the molecular ring, showing $\phi_0$ ($=ch/e$) flux-quantum periodicity. Though, conductance changes in the presence of transverse magnetic field, but the current-voltage characteristics are not significantly affected by this field.