Controlled complete suppression of single-atom inelastic spin and orbital cotunnelling

TL;DR

This study demonstrates how to completely suppress inelastic spin and orbital cotunnelling in a single magnetic atom by geometrically modifying its environment, enabling potential coherent spin control.

Contribution

It introduces a method to fully close inelastic tunnelling channels in single atoms through controlled structural changes, advancing quantum spin manipulation techniques.

Findings

Suppression of inelastic excitation signals in Co atoms on Cu₂N.

Structural transition affecting the d_z² orbital.

Effective cutoff of spin-flip cotunnelling path.

Abstract

The inelastic portion of the tunnel current through an individual magnetic atom grants unique access to read out and change the atom's spin state, but it also provides a path for spontaneous relaxation and decoherence. Controlled closure of the inelastic channel would allow for the latter to be switched off at will, paving the way to coherent spin manipulation in single atoms. Here we demonstrate complete closure of the inelastic channels for both spin and orbital transitions due to a controlled geometric modification of the atom's environment, using scanning tunnelling microscopy (STM). The observed suppression of the excitation signal, which occurs for Co atoms assembled into chain on a Cu$_2$N substrate, indicates a structural transition affecting the d$_z$$^2$ orbital, effectively cutting off the STM tip from the spin-flip cotunnelling path.