Efficient G₀W₀ and BSE calculations of heterostructures within an all-electron framework

The combination of two-dimensional materials into heterostructures offers new opportunities for the design of optoelectronic devices with tunable properties. However, computing electronic and optical properties of such systems using state-of-the-art methodology is challenging due to their large unit cells. This is in particular so for highly-precise all-electron calculations within the framework of many-body perturbation theory, which come with high computational costs. Here, we extend an approach that allows for the efficient calculation of the non-interacting polarizability, previously developed for planewave basis sets, to the (linearized) augmented planewave (L) APW method. This approach is based on an additive ansatz, which computes and superposes the polarizabilities of the individual components in their respective unit cells. We implement this formalism in the G₀W₀ module of the exciting code and implement an analogous approach for BSE calculations. This allows the calculation of highly-precise optical spectra at low cost. So-obtained results of the quasi-particle band structure and optical spectra are demonstrated for bilayer WSe₂ and pyridine@MoS₂ in comparison with exact reference calculations.