# Interfacial Hopping Integral as a Predictive Descriptor for Electron Transport: Saturated Alkane Junctions

## TL;DR

This paper introduces a new way to predict electron transport in molecular junctions by measuring the overlap between atomic orbitals at the interface.

## Contribution

The interfacial hopping integral (t_eld–mol) is proposed as a predictive descriptor for electron transport in molecular junctions.

## Key findings

- Conductance correlates with molecular tilt across π- and σ-type headgroups.
- A tight-binding model matches experimental results and generalizes to various molecular junctions.
- Variations in t_eld–mol explain different conductance sets in alkanedithiols.

## Abstract

Electron transport across interfaces governs a broad
range of fundamental
phenomena. Although orbital overlap is recognized as a key determinant,
its experimental quantification remains elusive. Here, we establish
the interfacial hopping integral (t
eld–mol), quantifying orbital overlap between contacting atoms, as a predictive
descriptor of single-molecule conductance in a benchmark domain of
saturated α,ω-functionalized alkane junctions. Using scanning
tunneling microscopy and molecular-junction mapping technique, we
correlate conductance with molecular tilt (tilt
mol) across π- and σ-type headgroups to extract t
eld–mol. We start with single-atom-thick
bismuth and lead adlayers on gold, with dominant p-character simpler than gold’s d-orbitals.
A tight-binding model incorporating Newns–Anderson–Grimley
theory yields conductance heatmaps that qualitatively match experiment
results and generalize to diverse molecular junctions. Applying this
model to the seminal case of alkanedithiols rationalizes literature
findings of one to three conductance sets by linking them to tilt
mol and corresponding t
eld–mol variations.