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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
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Long-range corrected exchange-correlation kernels to describe excitons in second-harmonic generation
Nicolas Gauriot1, Valérie Véniard2, Eleonora Luppi1
1Laboratoire de Chimie Théorique, Sorbonne Université and CNRS, F-75005 Paris, France.
The Journal of Chemical Physics
|December 23, 2019
Summary
Excitons significantly enhance second-harmonic generation (SHG) signals. This enhancement is linked to long-range corrected parameters and varies by material symmetry.
Area of Science:
- Condensed matter physics
- Materials science
- Quantum chemistry
Background:
- Second-harmonic generation (SHG) is a crucial nonlinear optical process.
- Understanding the role of electronic excitations, specifically excitons, is key to optimizing SHG.
- Accurate theoretical descriptions of electron correlation are needed to model excitonic effects.
Purpose of the Study:
- To investigate the influence of excitons on second-harmonic generation (SHG).
- To evaluate the performance of different long-range corrected (LRC) exchange-correlation kernels in describing excitons and their impact on SHG.
- To analyze the relationship between SHG enhancement and material symmetry.
Main Methods:
- Calculation of the macroscopic second-order nonlinear susceptibility (χ(2)) using LRC exchange-correlation kernels.
- Determination of the frequency-dependent macroscopic dielectric function (ϵM).
- Assessment across materials with cubic zincblende, hexagonal wurtzite, and tetragonal symmetries.
Main Results:
- Excitons play a significant role in enhancing the SHG signal.
- The magnitude of the long-range corrected alpha-parameter directly correlates with SHG enhancement.
- A material-dependent trend in SHG enhancement was observed.
Conclusions:
- Excitons are critical for achieving strong SHG signals.
- LRC kernels provide a valuable framework for studying excitonic contributions to nonlinear optics.
- The discovered trend offers a predictive tool for material selection in SHG applications.
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