Conductance of a molecular junction mediated by unconventional metal-induced gap states

TL;DR

This paper introduces a novel electron transport mechanism in molecular junctions, where surface states dominate conductance, enabling tunable electronic properties through gate voltage in a fullerene-nanotube system.

Contribution

It reveals that electrode surface states can dominate conductance, leading to metallization and tunability of molecular junctions, a departure from traditional charge-transfer or tunneling models.

Findings

Surface states induce significant conductance resonances.

Metallization of the molecular bridge occurs via surface states.

Conductance can be modulated with a gate voltage.

Abstract

The conductance of a molecular junction is commonly determined by either charge-transfer-doping, where alignment of the Fermi energy to the molecular levels is achieved, or tunnelling through the tails of molecular resonances within the highest-occupied and lowest-unoccupied molecular-orbital gap. Here, we present an alternative mechanism where electron transport is dominated by electrode surface states. They give rise to metallization of the molecular bridge and additional, pronounced conductance resonances allowing for substantial tailoring of its electronic properties via, e.g. a gate voltage. This is demonstrated in a field-effect geometry of a fullerene-bridge between two metallic carbon nanotubes.