Current shot noise in atomic contacts: Fe and FeH$_2$ between Au electrodes

TL;DR

This study investigates the shot noise and conductance properties of Fe and FeH$_2$ atomic contacts with gold electrodes, revealing spin-polarized transport and the influence of hydrogen on conductance behavior.

Contribution

It provides experimental measurements of shot noise and conductance in Fe and FeH$_2$ contacts, highlighting the role of hydrogen and spin polarization, supported by DFT calculations.

Findings

Fe and FeH$_2$ contacts show different conductance evolution.

FeH$_2$ exhibits up to 80% spin polarization at low conductance.

Hydrogen motion may significantly affect transport properties.

Abstract

Single Fe atoms on Au(111) surfaces were hydrogenated and dehydrogenated with the Au tip of a low-temperature scanning tunneling microscope (STM). Fe and FeH$_2$ were contacted with the tip of the microscope and show distinctly different evolutions of the conductance with the tip-substrate distance. The current shot noise of these contacts has been measured and indicates a single relevant conductance channel with the spin-polarized transmission. For FeH$_2$ the spin polarization reaches values up to 80\% for low conductances and is reduced if the tip-surface distance is decreased. These observations are partially reproduced using density functional theory (DFT) based transport calculations. We suggest that the quantum motion of the hydrogen atoms, which is not taken into account in our DFT modeling, may have a significant effect on the results.