Ab-initio investigation of Er3+ defects in tungsten disulfide

TL;DR

This study uses density functional theory to analyze erbium defects in monolayer tungsten disulfide, revealing their electronic properties and potential for quantum spin qubits in 2D materials.

Contribution

It provides the first ab-initio characterization of Er3+ defects in WS2, highlighting their electronic structure and optical transitions relevant for quantum applications.

Findings

Electrons localize at tungsten vacancies and Er3+ sites.

Defect states show low hybridization, resembling isolated Er3+ ions.

Identified optical transitions consistent with Er3+ luminescence.

Abstract

We use density functional theory (DFT) to explore the physical properties of an $Er_{ W}$ point defect in monolayer $WS_{ 2}$. Our calculations indicate that electrons localize at the dangling bonds associated with a tungsten vacancy ($V_{W}$) and at the $Er^{ 3+}$ ion site, even in the presence of a net negative charge in the supercell. The system features a set of intra-gap defect states, some of which are reminiscent of those present in isolated $Er^{ 3+}$ ions. In both instances, the level of hybridization is low, i.e., orbitals show either strong Er or W character. Through the calculation of the absorption spectrum as a function of wavelength, we identify a broad set of transitions, including one possibly consistent with the $Er^{ 3+}$ $4I_{ 15/2} \rightarrow 4I_{ 13/2}$ observed in other hosts. Combined with the low native concentration of spin-active nuclei as well as the two-dimensional nature of the host, these properties reveal $Er:WS_{ 2}$ as a potential platform for realizing spin qubits that can be subsequently integrated with other nanoscale optoelectronic devices.