Tailoring magnetism of nanographenes via tip-controlled dehydrogenation

TL;DR

This paper demonstrates a precise method using a scanning tunneling microscope tip to control the magnetism of nanographenes by site-specific dehydrogenation, enabling tailored spin states for potential quantum applications.

Contribution

It introduces a novel technique combining experimental manipulation and theoretical modeling to control nanographene magnetism through tip-controlled dehydrogenation.

Findings

Dehydrogenation forms Au-C bonds, altering the {c}lectron system.

Hybridization with substrate states eliminates unpaired {c}lectrons.

The method allows precise magnetic state manipulation of nanographenes.

Abstract

Atomically precise graphene nanoflakes, called nanographenes, have emerged as a promising platform to realize carbon magnetism. Their ground state spin configuration can be anticipated by Ovchinnikov-Lieb rules based on the mismatch of {\pi}-electrons from two sublattices. While rational geometrical design achieves specific spin configurations, further direct control over the {\pi}-electrons offers a desirable extension for efficient spin manipulations and potential quantum device operations. To this end, we apply a site-specific dehydrogenation using a scanning tunneling microscope tip to nanographenes deposited on a Au(111) substrate, which shows the capability of precisely tailoring the underlying {\pi}-electron system and therefore efficiently manipulating their magnetism. Through first-principles calculations and tight-binding mean-field-Hubbard modelling, we demonstrate that the dehydrogenation-induced Au-C bond formation along with the resulting hybridization between frontier {\pi}-orbitals and Au substrate states effectively eliminate the unpaired {\pi}-electron. Our results establish an efficient technique for controlling the magnetism of nanographenes.