First Principles Calculations of Temperature Dependent Exciton Binding Energies and Dissociation Rates in Semiconductors and Insulators

The development of new first principles methods capable to predict optical excitations in functional semiconductors and insulators under device operation conditions is of key importance. Standard state-of-the-art methods, such as the Bethe-Salpeter Equation, achieve excellent accuracy, but generally do not account for the effect of ionic vibrations and temperature.

In this talk, I will present a recent first principle framework that we have developed to understand the impact of ionic vibrations on the binding energy, fine structure and dissociation of excitons in semiconductors and insulators[1,2]. I will first introduce the theoretical background of this approach, from the point of view of scattering theory [3]. I will then describe our implementation, which uses the state-of-the-art Bethe-Salpeter equation framework [4] as a starting point [2]. In the second half of my talk I will give several examples from recent work that showcase this development, starting from simple applications of the theoretical approach within the Wannier-Mott and Frohlich models, and followed by examples of direct and fully converged first principles calculations of exciton binding energies and dissociation rates for binary and ternary semiconductors and insulators[1-3]. I will show how our recently developed framework allows us to compute temperature dependent exciton binding energies and exciton dissociation rates with good accuracy, and trends in agreement with experimental measurements.

[1] Filip, Haber & Neaton, Phys. Rev. Lett., 127, 067401 (2021).

[2] Alvertis, Haber, Li, Coveney, Louie, Filip & Neaton, Proc. Natl. Acad. Sci, 121, 30, e2403434121 (2024).

[3] Coveney, Haber, Alvertis, Neaton & Filip, Phys. Rev. B, 110, 5, 054307 (2024).

[4] Rohlfing & Louie, Phys. Rev. Lett. 81, 2312 (1998).