Exchange interaction and Fano resonances in diatomic molecular systems

TL;DR

This paper introduces a method using scanning tunneling microscopy to directly measure the exchange splitting in diatomic molecules by exploiting interference effects and Fano resonances caused by electron pathways.

Contribution

It presents a novel approach to measure exchange interactions in molecular systems through STM-induced interference effects and Fano resonances.

Findings

Identification of interference effects causing kinks in conductance

Demonstration of modulation of tunneling amplitudes by tip position

Linking Fano resonances to exchange splitting measurements

Abstract

We propose a mechanism to use scanning tunneling microscopy (STM) for direct measurements of the two-electron singlet-triplet exchange splitting $J$ in diatomic molecular systems, unsing the coupling between the molecule and the substrate electrons. The different pathways for electrons lead to interference effects and generate kinks in the differential conductance at the energies for the singlet and triplet states. These features are related to Fano resonance due to the branched electron wave functions. The ratio between the tunneling amplitudes through the two atoms can be modulated by spatial movements of the tip along the surface.