Exciton-to-Trion Conversion in Monolayer WS₂ under Pressure

Area of Science:

• Condensed Matter Physics
• Materials Science
• Optoelectronics

Background:

• Exciton-to-trion conversion in 2D semiconductors transitions optoelectronics from neutral bosons to charged fermions.
• This conversion impacts transport and spin/valley properties, previously induced via gate voltage, chemical doping, or nanoscale strain.
• Understanding this conversion is key for advanced semiconductor applications.

Purpose of the Study:

• To investigate the evolution of the photoluminescence spectrum of monolayer WS2 under high pressure.
• To decouple exciton and trion contributions by analyzing their responses to laser-power variations.
• To explore pressure-induced exciton-to-trion conversion mechanisms independent of external charge injection.

Main Methods:

• High-pressure photoluminescence spectroscopy of monolayer WS2.
• Analysis of spectral changes with varying laser power to distinguish exciton and trion contributions.
• Application of hydrostatic pressure up to several GPa.

Main Results:

• Crystal compression induces a partially reversible exciton-to-trion conversion in monolayer WS2.
• Trion recombination becomes dominant in photoluminescence emission above 3 GPa.
• The conversion mechanism is substrate-independent and driven by pressure-induced changes in intrinsic doping levels.

Conclusions:

• High pressure can effectively drive exciton-to-trion conversion in 2D materials without external charge injection.
• Modulating interatomic interactions via pressure reshapes the crystal potential, enabling trion-based emission.
• This offers a novel pathway for studying and controlling exciton-trion dynamics in 2D materials for future optoelectronics.