Single-electron transport in a molecular Hubbard dimer

TL;DR

This paper investigates single-electron tunneling in a molecular system modeled by the Hubbard dimer, revealing the significance of electron-electron interactions in molecular electronic transport.

Contribution

It demonstrates the applicability of the Hubbard dimer model to describe electron transport in a molecular system and measures key interaction energies experimentally.

Findings

Electron-electron repulsion energies match density functional calculations.

Transport behavior aligns with Hubbard model predictions.

Gate-dependent rectification confirms model-based selection rules.

Abstract

Many-body electron interactions are at the heart of chemistry and solid-state physics. Understanding these interactions is crucial for the development of molecular-scale quantum and nanoelectronic devices. Here, we investigate single-electron tunneling through an edge-fused porphyrin oligomer and demonstrate that its transport behavior is well described by the Hubbard dimer model. This allows us to study the role of electron-electron interactions in the transport setting. In particular, we empirically determine the molecule's on-site and inter-site electron-electron repulsion energies, which are in good agreement with density functional calculations, and establish the molecular electronic structure within various charge states. The gate-dependent rectification behavior is used to further confirm the selection rules and state degeneracies resulting from the Hubbard model. We therefore demonstrate that current flow through the molecule is governed by a non-trivial set of vibrationally coupled electronic transitions between various many-body states, and experimentally confirm the importance of electron-electron interactions in single-molecule devices.