TY  - JOUR
PB  - SciPost Foundation
DO  - 10.21468/SciPostPhys.19.5.129
TI  - A real-time approach to frequency-mixing spectroscopies: Application to sum and difference frequency generation in two-dimensional crystals
PY  - 2025/11/18
UR  - https://www.scipost.org/SciPostPhys.19.5.129
JF  - SciPost Physics
JA  - SciPost Phys.
VL  - 19
IS  - 5
SP  - 129
A1  - Pionteck, Mike N.
AU  - Grüning, Myrta
AU  - Sanna, Simone
AU  - Attaccalite, Claudio
AB  - We propose a computational framework to extract nonlinear response functions from real-time simulations in the presence of more than one external field. We apply this approach to the calculation of sum frequency generation (SFG) and difference frequency generation (DFG). SFG and DFG are second-order nonlinear processes where two lasers with frequencies $\omega_1$ and $\omega_2$ combine to produce a response at frequency $\omega = \omega_1 ± \omega_2$. Compared with other nonlinear responses such as second-harmonic generation, SFG and DFG allow for tunability over a larger range. Moreover, the optical response can be enhanced by selecting the two laser frequencies in order to match specific electron-hole transitions. To assess the approach, we calculate the SFG and DFG of two-dimensional crystals, h-BN and MoS$_2$ monolayers, from real-time solution of an effective Schrödinger equation. Within the effective Schrödinger equation, one can select from various levels of theory for the effective one-particle Hamiltonian to account for local-field effects and electron-hole interactions. We compare results obtained within the independent particle picture and including many-body effects. Such comparison allows us to identify and characterize excitonic features in the obtained spectra. Additionally, we demonstrate that our approach can also extract higher-order response functions, such as field-induced second-harmonic generation. We provide an example using the h-BN bilayer.
ER  -

@Article{10.21468/SciPostPhys.19.5.129,
	title={{A real-time approach to frequency-mixing spectroscopies: Application to sum and difference frequency generation in two-dimensional crystals}},
	author={Mike N. Pionteck and Myrta Grüning and Simone Sanna and Claudio Attaccalite},
	journal={SciPost Phys.},
	volume={19},
	pages={129},
	year={2025},
	publisher={SciPost},
	doi={10.21468/SciPostPhys.19.5.129},
	url={https://scipost.org/10.21468/SciPostPhys.19.5.129},
}