Giant spin-orbit splitting of point defect states in monolayer WS$_2$

TL;DR

This study reveals that point defects in monolayer WS₂ exhibit significantly enhanced spin-orbit splitting, with potential implications for spintronics, by analyzing defect types, formation energies, and SOC effects.

Contribution

The paper demonstrates that point defects in monolayer WS₂ cause giant spin-orbit splitting and magnetic moments, providing new insights into defect-induced spin phenomena in TMDs.

Findings

Defects like V_S and antisites show up to 296 meV SOC splitting.

W_S and W_S2 antisites have magnetic moments of 2 μ_B.

SOC effects can increase or decrease defect state splitting depending on their position.

Abstract

The spin-orbit coupling (SOC) effect has been known to be profound in monolayer pristine transition metal dichalcogenides (TMDs). Here we show that point defects, which are omnipresent in the TMD membranes, exhibit even stronger SOC effects and change the physics of the host materials drastically. In this Article we chose the representative monolayer WS\sub{2} slabs from the TMD family together with seven typical types of point defects including monovacancies, interstitials, and antisites. We calculated the formation energies of these defects, and studied the effect of spin-orbit coupling (SOC) on the corresponding defect states. We found that the S monovacancy (V\sub{S} ) and S interstitial (adatom) have the lowest formation energies. In the case of V\sub{S} and both of the W\sub{S and W\sub{S2} antisites, the defect states exhibit giant splitting up to 296 meV when SOC is considered. Depending on the relative position of the defect state with respect to the conduction band minimum (CBM), the hybrid functional HSE will either increase the splitting by up to 60 meV (far from CBM), or decrease the splitting by up to 57 meV (close to CBM). Furthermore, we found that both the W\sub{S} and W\sub{S2} antisites possess a magnetic moment of 2 $\mu_{B}$ localized at the antisite W atom and the neighboring W atoms. All these findings provide new insights in the defect behavior under SOC point to new possibilities for spintronics applications for TMDs.