Tightly bound excitons in monolayer WSe(2)

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Optics

Background:

• Exciton binding energies in semiconductor quantum wells are typically small.
• Understanding excited states is crucial for optoelectronic applications.

Purpose of the Study:

• To investigate exciton binding energy and excited states in tungsten diselenide (WSe2) monolayers.
• To compare experimental findings with theoretical models like the 2D hydrogenic model.

Main Methods:

• Combined linear absorption spectroscopy.
• Two-photon photoluminescence excitation spectroscopy.

Main Results:

• Determined exciton binding energy in WSe2 monolayers to be 0.37 eV.
• Observed exciton excited states are visible even at room temperature.
• The exciton excitation spectrum deviates from the 2D hydrogenic model, indicating reduced dielectric screening.

Conclusions:

• Reduced and nonlocal dielectric screening of Coulomb interactions in 2D semiconductors.
• The large exciton binding energy in WSe2 has significant implications for next-generation photonics and optoelectronics.