Tracking the origin of single photon emitters in WSe₂

Single photon emitters (SPE) in WSe₂ have been investigated in several recent publications [1, 2], receiving considerable attention in the field of two-dimensional materials. Although the origin of these emitters is generally attributed to defects and/or local strain, an exact microscopic
explanation has proven elusive.
Using a multiscale approach we established a tight-binding model capturing non-uniform strain, defects and coulomb-interactions we elucidate this mystery. Tight-binding calculations with local strain patterns and open boundary conditions for a large WSe₂ flake yield quantum-dot-like localization. Including defects we can reproduce and explain the large g-factor (≈ 9) as well as the zero field splitting, the linear polarization and the electric field dependence.
We conclude that local strain shifts excitonic energy levels into an energy of otherwise unoccupied inter-gap defect states, acting as a doorkeeper to fill these states. Together with localized
valence bands, this leads to sharp SPE.





[1] P. Tonndorf, et.al., "Single-photon emission from localized excitons in an atomically thin semiconductor", Optica, 2, 347-352, (2015).
[2] Koperski M., et.al., ”Single photon emitters in exfoliated WSe 2 structures”,Nature Nano, 10, 503-605, (2015).