Charge State-Dependent Symmetry Breaking of Atomic Defects in Transition Metal Dichalcogenides

TL;DR

This study uses advanced microscopy techniques to directly observe how the charge state of atomic defects in MoS₂ influences local symmetry breaking, revealing effects like Jahn-Teller distortions that impact quantum emitter properties.

Contribution

It provides direct imaging and analysis of charge state-dependent symmetry breaking in atomic defects within transition metal dichalcogenides, highlighting the role of Jahn-Teller effects.

Findings

Charge states induce local lattice distortions.

Symmetry breaking varies with defect charge state.

Electronic and geometric structures are disentangled.

Abstract

The functionality of atomic quantum emitters is intrinsically linked to their host lattice coordination. Structural distortions that spontaneously break the lattice symmetry strongly impact their optical emission properties and spin-photon interface. Here we report on the direct imaging of charge state-dependent symmetry breaking of two prototypical atomic quantum emitters in mono- and bilayer MoS$_2$ by scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM). By substrate chemical gating different charge states of sulfur vacancies (Vac$_\text{S}$) and substitutional rhenium dopants (Re$_\text{Mo}$) can be stabilized. Vac$_\text{S}^{-1}$ as well as Re$_\text{Mo}^{0}$ and Re$_\text{Mo}^{-1}$ exhibit local lattice distortions and symmetry-broken defect orbitals attributed to a Jahn-Teller effect (JTE) and pseudo-JTE, respectively. By mapping the electronic and geometric structure of single point defects, we disentangle the effects of spatial averaging, charge multistability, configurational dynamics, and external perturbations that often mask the presence of local symmetry breaking.