Second-harmonic generation in 2D semiconductors via the time-dependent adiabatic GW method: the role of electron-hole interactions

In this work, we use a first-principles, interacting Green’s functions approach within the time domain to study the non-linear optical response of 2D semiconductors. We employ the recently developed time-dependent adiabatic GW (TD-aGW) approach, which correctly captures quasiparticle excitations within the fully dynamical GW approximation at equilibrium and produces the same linear response given by the GW-BSE approach with a statically screened electron-hole interaction kernel [1, 2]. Beyond the linear regime, this approach also allows us to naturally obtain higher-harmonic responses and including excitonic effects. As an application, we compute the second harmonic generation (SHG) coefficient , associated with the second-order susceptibility tensor, and higher-order responses. We survey the SHG in a few 2D semiconductors of interest, such as transition metal dichalcogenides (TMDCs) of different band topologies, and discuss the role of the electron-hole interaction in the spectra. Considering its importance on the linear response of low-dimensional systems, we expect excitonic effects to be relevant to higher-order responses functions, as suggested in earlier calculations [1, 3, 4]. Besides promoting a deeper understanding of the optical properties of known materials, these calculations suggest methods to tune many-body interactions and the resulting nonlinear optical properties of low-dimensional materials.

References:

[1] Yang Hao Chan, Diana Y. Qiu, Felipe H. da Jornada, and Steven G. Louie. Proc. Natl. Acad. Sci. U. S. A., 118(25):1–5, 2021.

[2] C. Attaccalite, M. Gruning, and A. Marini. Phys. Rev. B - Condens. Matter Mater. Phys., 84(24):1–10, 2011.

[3] M. Gruning and C. Attaccalite. Phys. Rev. B - Condens. Matter Mater. Phys., 89(8):1–5, 2014.

[4] Yadong Wei, Xiaodong Xu, Songsong Wang, Weiqi Li and Yongyuan Jiang, Phys. Chem. Chem. Phys., 2019,21, 21022-21029.