Anomalously polarised emission from a MoS₂/WS₂ heterostructure

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Van der Waals heterostructures (HS) offer unique electronic and optical properties.
• Transition metal dichalcogenides (TMDs) like MoS2 and WS2 are key components in advanced electronic devices.

Purpose of the Study:

• To investigate circularly polarized emission in a MoS2/WS2 van der Waals heterostructure.
• To elucidate the mechanism behind cross-polarized light emission.
• To understand the role of charge transfer and doping in optical properties.

Main Methods:

• Fabrication of a van der Waals heterostructure comprising monolayer MoS2 and trilayer WS2.
• Selective optical excitation of the MoS2 layer.
• Analysis of circularly polarized emission spectra.
• Rate equation modeling to simulate electron transitions.

Main Results:

• Observed circularly polarized emission with helicity opposite to optical excitation.
• Confirmed charge transfer from WS2 to MoS2 as the source of cross-polarized emission.
• Identified n-doping due to sulfur vacancies and defects as a key factor enhancing electron transition rates.

Conclusions:

• The study demonstrates a novel mechanism for generating circularly polarized light in TMD heterostructures.
• Defect-induced charge transfer and inter-valley electron transitions are crucial for this phenomenon.
• Findings provide insights for designing optoelectronic devices with tailored polarization control.