Speaker
Description
We review here our achievements in the field of excitons in van der Waals (vdW) heterostructures of two-dimensional (2D) materials from the last few years. Electron-electron and electron-hole (exciton) effects are specifically pronounced in 2D materials and their vdW heterostructures due to weak dielectric screening from the environment. These heterostructures offer a versatile platform for engineering excitonic and optoelectronic properties. However, accurate prediction of their behavior is non-trivial. We show that a) advanced many-body methods are indispensable for these systems [1]; b) reliance on standard commensurate models introduces artificial strain, creating a significant risk of misattributing computational artifacts to intrinsic interface physics [2]; and c) in certain vdW heterostructures, the emergence and energy of interlayer excitons depend sensitively and predictably on the stacking order [3]. From a computational point of view, our work uses very accurate many-body methods (GW, BSE, TD-DFT) to resolve subtle physical effects between and within layers. We proved these techniques to be precise at the experimental level or compatible with independent stochastic approaches (QMC), also for 2D materials [4-7]. Our findings highlight how stacking-dependent interlayer coupling governs key excitonic properties of vdW heterostructures, allowing targeted manipulation for tailored next-generation light-harvesting and quantum technologies.
[1] Ketolainen T., Macháčová N., Karlický F.: Optical Gaps and Excitonic Properties of 2D Materials by Hybrid TD-DFT: Evidences for Monolayers and Prospects for vdW Heterostructures. J. Chem. Theory Comput. 16 (2020) 5876
[2] Macháčová N., Kalmár J., Karlický F.: Excitonic landscape and quasi-type-I nature of incommensurate Ti-based MXene/MoS$_2$ van der Waals heterostructures. Under review (2026)
[3] Kumar N., Kolos M., Karlický F.: Stacking-Dependent Interlayer Excitons in BP/CrSe$_2$ van der Waals Heterostructure. Nano Lett. 25 (2025) 16608
[4] Kolos M., Karlický F.: Predicting Fundamental Gaps of Chromium-Based 2D Materials Using GW Methods. J. Phys. Chem. C 129 (2025) 2782
[5] Kumar N., Karlický F.: Oxygen-terminated Ti$_3$C$_2$ MXene as an excitonic insulator. Appl. Phys. Lett. 122 (2023) 183102
[6] Dubecký M., Karlický F., Minárik S., Mitas L.: Fundamental gap of fluorographene by many-body GW and fixed-node diffusion Monte Carlo methods. J. Chem. Phys. 153 (2020) 184706
[7] Dubecký M., Minárik S., Karlický F.: Benchmarking fundamental gap of Sc$_2$C(OH)$_2$ MXene by many-body methods. J. Chem. Phys. 158 (2023) 054703
Acknowledgements: This contribution has been produced with the financial support of the European Union under the LERCO project (number CZ.10.03.01/00/22_003/0000003) via the Operational Programme Just Transition.