Interlayer excitons in bilayer MoS₂ under uniaxial tensile strain

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Atomically thin transition metal dichalcogenides (TMDCs) possess unique mechanical and optical properties, including flexibility and strong optical absorption.
• Excitons, bound electron-hole pairs, in TMDCs are sensitive to mechanical strain, affecting their energy and line width.
• Interlayer excitons, with electrons and holes in different layers, have recently been observed in bilayer MoS2 at room temperature.

Purpose of the Study:

• To investigate the behavior of interlayer excitons in bilayer MoS2 under uniaxial tensile strain.
• To quantify the energy shift of interlayer excitons in response to applied strain.
• To confirm the origin of interlayer excitons and explore their potential for straintronic applications.

Main Methods:

• Fabrication of bilayer MoS2 samples.
• Application of uniaxial tensile strain up to 1.6% to the bilayer MoS2.
• Measurement of differential transmission spectra at various strain levels.

Main Results:

• The energy of interlayer excitons in bilayer MoS2 shifts with applied uniaxial tensile strain.
• A gauge factor of -47 meV/% was derived for the interlayer exciton energy shift, comparable to intralayer excitons.
• The findings confirm the K-point origin of interlayer excitons, with electrons in one layer and holes delocalized across both layers.

Conclusions:

• Interlayer excitons in bilayer MoS2 exhibit significant strain-dependent energy shifts.
• The observed strain response is consistent with theoretical predictions and comparable to intralayer excitons.
• This research provides a foundation for developing future straintronic devices utilizing interlayer excitons in TMDCs.