Strong polarization-induced reduction of addition energies in single-molecule nanojunctions

TL;DR

This paper investigates how polarization effects significantly reduce addition energies in single-molecule transistors by combining quantum chemistry with environmental screening, explaining experimental observations.

Contribution

It introduces a combined quantum chemical and screening model to explain polarization-induced energy level shifts and reduction of addition energies in molecular junctions.

Findings

Large reduction of addition energy observed

Electrostatic charging energy decreases due to polarization

Charge stability diagrams qualitatively match experiments

Abstract

We address polarization-induced renormalization of molecular levels in solid-state based single-molecule transistors and focus on an organic conjugate molecule where a surprisingly large reduction of the addition energy has been observed. We have developed a scheme that combines a self-consistent solution of a quantum chemical calculation with a realistic description of the screening environment. Our results indeed show a large reduction, and we explain this to be a consequence of both (a) a reduction of the electrostatic molecular charging energy and (b) polarization induced level shifts of the HOMO and LUMO levels. Finally, we calculate the charge stability diagram and explain at a qualitative level general features observed experimentally.