Optical Absorption and Photoluminescence of Single-Layer Boron Nitride from a First-Principles Cumulant Approach

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Physics

Background:

• The photoluminescence spectrum of single-layer boron nitride (h-BN monolayer) exhibits unexplained features attributed to exciton-phonon coupling.
• Understanding these interactions is crucial for interpreting experimental data and predicting material properties.

Purpose of the Study:

• To calculate and interpret the optical absorption and photoluminescence spectra of h-BN monolayer.
• To identify specific exciton-phonon scattering channels and their influence on spectral features.
• To investigate the role of electron-hole interactions and Frölich interaction in h-BN monolayer.

Main Methods:

• First-principles calculations.
• Many-body cumulant expansion of charge response.
• Analysis of exciton-phonon scattering channels.

Main Results:

• Calculated optical absorption and photoluminescence spectra for h-BN monolayer.
• Identified specific exciton-phonon scattering mechanisms responsible for spectral features.
• Demonstrated cancellation of Frölich interaction at small phonon momenta due to electron-hole interactions.

Conclusions:

• The study provides a theoretical interpretation of experimental photoluminescence spectra in h-BN monolayer.
• Accurate calculations require preserving the invariance of exciton-phonon matrix elements under unitary transformations.
• This work advances the understanding of light-matter interactions in 2D materials.