Electronic and magnetic properties of single chalcogen vacancies in MoS$_2$/Au(111)

TL;DR

This study investigates how sulfur vacancies in monolayer MoS$_2$ on Au(111) influence electronic and magnetic properties, revealing charge states and Kondo resonances that can be tuned via defect engineering.

Contribution

It demonstrates that sulfur vacancies induce magnetic moments and Kondo effects in MoS$_2$, showing how defect engineering can control magnetic properties in 2D materials.

Findings

S vacancies are negatively charged and exhibit Kondo resonance.

The exchange coupling strength varies with the moiré structure.

Charge neutrality is maintained without hybridization with the substrate.

Abstract

Two-dimensional (2D) transition-metal dichalcogenides (TMDC) are considered highly promising platforms for next-generation optoelectronic devices. Owing to its atomically thin structure, device performance is strongly impacted by a minute amount of defects. Although defects are usually considered to be disturbing, defect engineering has become an important strategy to control and design new properties of 2D materials. Here, we produce single S vacancies in a monolayer of MoS$_2$ on Au(111). Using a combination of scanning tunneling and atomic force microscopy, we show that these defects are negatively charged and give rise to a Kondo resonance, revealing the presence of an unpaired electron spin exchange coupled to the metal substrate. The strength of the exchange coupling depends on the density of states at the Fermi level, which is modulated by the moir\'e structure of the MoS$_2$ lattice and the Au(111) substrate. In the absence of direct hybridization of MoS$_2$ with the metal substrate, the S vacancy remains charge-neutral. Our results suggest that defect engineering may be used to induce and tune magnetic properties of otherwise non-magnetic materials.