Localized Intervalley Defect Excitons as Single-Photon Emitters in WSe_{2}.

Area of Science:

• Quantum technology materials
• Condensed matter physics
• Computational materials science

Background:

• Single-photon emitters are crucial for quantum technologies.
• Monolayer tungsten diselenide (WSe_{2}) is a promising single-photon source candidate.
• The microscopic origins of WSe_{2} single-photon emission remain unclear.

Purpose of the Study:

• To elucidate the microscopic mechanisms behind single-photon emission in WSe_{2}.
• To investigate the role of strain and defects in WSe_{2} optical properties.
• To identify the specific states responsible for antibunched single-photon emission.

Main Methods:

• Multiscale tight-binding simulations.
• Bethe-Salpeter equation calculations.
• Modeling of WSe_{2} under nonuniform strain and point defects.

Main Results:

• Strain shifts excitonic levels into the band gap, overlapping with defect states.
• Hybridization of these states enables efficient filling and radiative decay.
• Intervalley defect excitonic states are identified as the source of single-photon emission.

Conclusions:

• The proposed model explains experimental observations like brightness and field dependencies.
• This work clarifies the origin of single-photon emission in WSe_{2}.
• Findings pave the way for optimized quantum light sources based on WSe_{2}.