Quadrupolar and Dipolar Excitons in Bilayer 2H-MoSe_{2}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Optics

Background:

• Bilayer molybdenum diselenide (MoSe2) exhibits complex excitonic properties.
• Understanding exciton behavior in layered materials is crucial for novel electronic and optoelectronic devices.

Purpose of the Study:

• To experimentally observe and characterize quadrupolar exciton states in 2H-stacked bilayer MoSe2.
• To investigate the influence of external electric and magnetic fields on these quadrupolar exciton states.
• To elucidate the underlying mechanisms governing the field-dependent behavior of quadrupolar excitons.

Main Methods:

• Experimental observation using reflectance contrast spectroscopy.
• Application of vertical electric fields to induce energy shifts.
• Helicity-resolved reflectance contrast measurements under electric and magnetic fields.
• Comparison with a phenomenological coupled-oscillator model.

Main Results:

• Experimental observation of quadrupolar exciton states in bilayer MoSe2.
• A quadratic energy redshift of quadrupolar excitons under an applied vertical electric field.
• Linear energy splitting of coexisting dipolar excitons under the same field.
• Field-dependent spin and valley configurations attributed to interlayer exciton hybridization.

Conclusions:

• Bilayer MoSe2 serves as a promising platform for exploring electric-field-tunable many-body exciton phenomena.
• The observed behavior is explained by the hybridization of spin-triplet interlayer excitons.
• This study provides insights into the fundamental physics of excitons in van der Waals heterostructures.