Second Harmonic Generation Susceptibilities from Symmetry Adapted Wannier Functions

Area of Science:

• Materials Science
• Quantum Chemistry
• Solid-State Physics

Background:

• Second Harmonic Generation (SHG) is a crucial nonlinear optical phenomenon.
• Determining the orbital-level origins of SHG has been a persistent challenge in materials science.
• Identifying local contributions to SHG is essential for designing new materials.

Purpose of the Study:

• To develop a first-principles computational approach for elucidating the orbital-level origin of SHG.
• To quantify the contributions of individual orbitals and atoms to the SHG response.
• To apply the method to known SHG materials and validate its predictive power.

Main Methods:

• Development of a first-principles method utilizing symmetry-adapted Wannier functions.
• Evaluation of SHG contributions at the atomic and orbital levels.
• Application to benchmark SHG materials: KBe2BO3F2, KCaCO3F, and β-BaB2O4.

Main Results:

• The method successfully quantifies orbital and atomic contributions to SHG without empirical parameters.
• Noncentrosymmetric sublattices are identified as the primary source of the SHG effect.
• The energy levels of these specific orbitals directly correlate with the magnitude of the SHG response.

Conclusions:

• This first-principles approach provides unprecedented insight into the microscopic origins of SHG.
• The findings highlight the critical role of specific orbitals in noncentrosymmetric materials for SHG.
• The method offers a pathway for the rational design of materials with enhanced nonlinear optical properties.