Non-trivial length dependence of the conductance and negative differential resistance in atomic molecular wires

TL;DR

This study investigates the electronic transport properties of two novel atomic chain molecular wires, revealing length-independent conductance, negative differential resistance phenomena, and the ability to modulate these effects via gating.

Contribution

It introduces two new molecular wire systems with unique length and bias-dependent conductance and NDR behaviors, including a novel NDR mechanism linked to LUMO resonance movement.

Findings

Benzene-thiol-capped chains have higher conductance than pyridine-capped ones.

Conductance remains nearly constant regardless of molecular length.

Gating can eliminate NDR and significantly alter I-V characteristics.

Abstract

We study the electronic and transport properties of two novel molecular wires made of atomic chains of carbon atoms (polyynes) capped with either, benzene-thiols or pyridines. While both molecules are structurally similar, the electrical conductance of benzene-thiol-capped chains attached to gold electrodes is found to be much higher than that of pyridine-capped chains. We predict that the conductance is almost independent of molecular length, which suggests that these molecules could be ideal molecular wires for sub-10 nm circuitry. Both systems exhibit negative differential resistance (NDR) but its origin and characteristics depend on the type of molecule. We find a novel type of NDR mechanism produced by the movement of the LUMO resonance with bias. We also show that by gating the pyridine-capped molecules it is possible to make the NDR disappear and dramatically modify the $I$-$V$ characteristics and the length dependence.