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Updated: Jun 7, 2025
08:04
Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
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Exciton Enhanced Nonlinear Optical Responses in Monolayer h-BN and MoS2: Insight from First-Principles Exciton-State
Jiawei Ruan1,2, Yang-Hao Chan3,4, Steven G Louie1,2
1Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States.
Nano Letters
|November 18, 2024
Summary
This study introduces a new method to understand how excitons influence nonlinear optical properties in 2D materials. Strong excitonic effects require bright excitons that can couple effectively, explaining observed differences in h-BN and MoS2.
Area of Science:
- Materials Science
- Quantum Mechanics
- Optics
Background:
- Excitons are crucial for understanding the photophysics of low-dimensional materials.
- Quantifying excitonic effects in nonlinear optical (NLO) processes is complex.
- Previous studies often lack detailed analysis of individual excitonic state contributions.
Purpose of the Study:
- To develop an ab initio approach for calculating second-order NLO responses, including excitonic effects.
- To analyze the specific role of individual excitonic states in NLO processes.
- To investigate the NLO responses of monolayer hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2).
Main Methods:
- Employed an exciton-state coupling formalism within an ab initio framework.
- Calculated the second harmonic generation (SHG) susceptibility.
- Calculated the shift current conductivity tensor.
Main Results:
- Identified that strong excitonic enhancement in NLO responses necessitates optically bright excitons with strong coupling to other bright excitons.
- Explained the presence of two prominent peaks in the SHG of monolayer h-BN.
- Showed that A and B excitons in MoS2 exhibit minimal excitonic enhancement in both SHG and shift current generation.
Conclusions:
- The developed method provides a detailed understanding of excitonic contributions to NLO phenomena.
- The findings clarify the differing NLO behaviors observed in h-BN and MoS2 based on exciton properties.
- This work offers insights into designing 2D materials with tailored NLO functionalities.
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