Quantum transport through STM-lifted single PTCDA molecules

TL;DR

This study investigates quantum conductance in single PTCDA molecules using STM, revealing a conductance resonance at the Fermi level and analyzing how molecular junction configurations affect transport properties.

Contribution

The paper combines experimental STM measurements with theoretical calculations to analyze quantum transport through PTCDA molecules, highlighting the impact of tip-surface distance on conductance resonance.

Findings

Conductance resonance appears at the Fermi level for certain tip-surface distances.

The molecular chemisorption level shifts and sharpens with increasing tip-surface distance.

Experimental results agree with Landauer/Keldysh transport calculations.

Abstract

Using a scanning tunneling microscope we have measured the quantum conductance through a PTCDA molecule for different configurations of the tip-molecule-surface junction. A peculiar conductance resonance arises at the Fermi level for certain tip to surface distances. We have relaxed the molecular junction coordinates and calculated transport by means of the Landauer/Keldysh approach. The zero bias transmission calculated for fixed tip positions in lateral dimensions but different tip substrate distances show a clear shift and sharpening of the molecular chemisorption level on increasing the STM-surface distance, in agreement with experiment.