Exciton (De)Localization and Dissociation in Heterogeneous Semiconductors from First Principles Computational Modeling

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• Prof. Marina Filip (Oxford)
• Thursday 12 June 2025, 14:00-15:30
• Seminar Room 3, RDC.

If you have a question about this talk, please contact Bo Peng.

Understanding the physics of how excitons form, delocalize and dissociate is of key importance to the functionality of a wide range of applications, such as photovoltaics, lighting and lasing. Development of new computational modeling techniques based on density functional theory (DFT) and many body perturbation theory capable to describe interactions between excitons and other quasiparticles constitutes a frontier first principles computational modeling of materials. The GW+Bethe-Salpeter Equation (BSE) approach [1,2] is the state-of-the-art approach to compute optical excitation energies in semiconductors and insulators and provides the foundation of new methods aimed at describing complex excited state phenomena.

In the first part of my talk, I will present a new methodological development that generalizes the BSE to include the impact of ionic vibrations on the dielectric screening of excitons [3,4], and show how this allows us to compute temperature dependent exciton binding energies, as well the rate of dissociation of excitons upon scattering with phonons in several examples of semiconductors and insulators including III -V semiconductors and the ternary oxide BiVO4 [4,5]. In the second part of my talk (as time allows), I will present our recent study of layered halide perovskites and hetero-structures [6-9]. In particular, I will discuss our recent work focused on understanding the mechanism for tuning the inter-layer exciton de-localization in these complex heterogeneous semiconductors, as predicted by our first principles calculations.

1. Hybertsen & Louie, Phys. Rev. B 34 , 5390 (1986). 2. Rohlfing & Louie, Phys. Rev. Lett. 81, 2312 (1998). 3. Filip, Haber & Neaton, Phys. Rev. Lett. 127, 67401 (2021). 4. Alvertis, Haber, Li, Coveney, Louie, Filip & Neaton, Proc. Natl. Acad. Sci 121 (30), e2403434121 (2024). 5. Gant, Alvertis, Coveney, Haber, Filip & Neaton, arXiv:2504.00110 (2025). 6. Coveney, Haber, Alvertis, Neaton & Filip, Phys. Rev. B 110 (5), 054307 (2023). 7. Filip, Qiu, Del Ben & Neaton, Nano Lett. 22 (12), 4870-4878 (2022). 8. McArthur, Filip & Qiu, Nano Lett. 23 (9), 3796-3802 (2023). 9. Chen & Filip, J. Phys. Chem. Lett. 14, 47, 10634-10641 (2023).

This talk is part of the Theory of Condensed Matter series.

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