Excitonic effects on the linear and nonlinear optical properties of solid C60 fullerene, insights from many-body first-principles calculations

We perform the many-body Bethe-Salpeter equation eigenstates based sum-over-states calculations for the linear and nonlinear optical properties of solid C60 fullerene. Excitonic and local field effects are included in the calculations. We calculate the one-photon absorption (OPA), third harmonic generation (THG), degenerate four-wave mixing (DFWM), and electric-field-induced second harmonic generation (ESHG) spectra of solid C60 fullerene. The overall agreement between the theoretical and experimental results is good for all calculated spectra. The OPA spectrum shows that the solid C60 fullerene has a large excitonic binding energy of 0.35 eV. The position and intensity of spectral peaks are modified significantly. By tracing the sum-over-states progress, we determine the type of nonlinear polarization resonances for the characteristic peaks of the THG process, which may clear up a discrepancy in two experimental results. The calculated DFWM spectrum is in excellent agreement with the available experimental results in terms of line shape and peak positions, and thus the two-photon absorption peaks can be well understood on the basis of the excitonic states of solid C60 fullerene. The dynamic ESHG spectrum is given as a reference for the future experiment. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study performs calculations based on the many-body Bethe-Salpeter equation eigenstates for the linear and nonlinear optical properties of solid C60 fullerene, including OPA, THG, DFWM, and ESHG spectra. The overall agreement between theoretical and experimental results is good, and the type of nonlinear polarization resonances for characteristic peaks of the THG process was determined. The DFWM spectrum shows excellent agreement with available experimental results in terms of line shape and peak positions.