Excitonic effects on the silicon plasmon resonance

Area of Science:

• Condensed matter physics
• Materials science
• Computational physics

Background:

• The electron energy loss spectrum (EELS) provides insights into the electronic properties of materials.
• Accurate theoretical modeling of EELS requires incorporating various electronic correlations.

Purpose of the Study:

• To perform an ab initio calculation of silicon's electron energy loss spectrum.
• To investigate the impact of local-field, self-energy, and excitonic effects on EELS.
• To achieve high accuracy in theoretical predictions by comparing with experimental data.

Main Methods:

• Ab initio calculations were employed to simulate the electron energy loss spectrum.
• The study incorporated local-field effects, self-energy corrections, and excitonic (electron-hole interaction) effects.
• The random phase approximation (RPA) was used as a baseline for comparison.

Main Results:

• Standard self-energy corrections, when added to the random phase approximation (RPA), degraded the plasmon resonance line shape.
• The inclusion of electron-hole interactions effectively canceled the detrimental effects of self-energy corrections.
• The combined theoretical approach yielded excellent agreement with experimental EELS data for silicon.

Conclusions:

• Electron-hole interactions are crucial for accurately predicting the electron energy loss spectrum of silicon.
• A comprehensive theoretical model including local-field, self-energy, and excitonic effects is necessary for quantitative agreement with experiments.
• The study highlights the importance of considering the mixing of interband transitions across positive and negative frequencies.