Phonon screening of excitons in semiconductors: halide perovskites and beyond

Journal article

The ab initio Bethe-Salpeter equation (BSE) approach, an established method for the study of excitons in materials, is typically solved in a limit where only static screening from electrons is captured. Here, we generalize this framework to include dynamical screening from phonons at lowest order in the electron-phonon interaction. We apply this generalized BSE approach to a series of inorganic lead halide perovskites, CsPbX₃, with X = Cl, Br, and I. We find that inclusion of screening from phonons significantly reduces the computed exciton binding energies of these systems. By deriving a simple expression for phonon screening effects, we reveal general trends for their importance in semiconductors and insulators, based on a hydrogenic exciton model. We demonstrate that the magnitude of the phonon screening correction in isotropic materials can be reliably predicted using four material specific parameters: the reduced effective mass, static and optical dielectric constants, and frequency of the most strongly coupled longitudinal-optical phonon mode. This framework helps to elucidate the importance of phonon screening and its relation to excitonic properties in a broad class of semiconductors.

Authors: Filip, MR; Haber, JB; Neaton, JB

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review Letters
• Volume: 127
• Issue: 6
• Article number: 067401
• Place of publication: United States
• Publication date: 2021-08-05
• Acceptance date: 2021-06-04
• DOI: 10.1103/physrevlett.127.067401
• EISSN: 1079-7114
• ISSN: 0031-9007
• Pmid: 34420331
• Language: English
• Keywords: FFR