Giant Fine Structure Splitting of the Bright Exciton in a Bulk MAPbBr$_3$ Single Crystal

TL;DR

This study reports the first observation of significant bright exciton fine structure splitting in a bulk perovskite crystal, revealing intrinsic properties unaffected by quantum confinement, with implications for understanding nanocrystal behavior.

Contribution

It demonstrates the existence of large exciton fine structure splitting in bulk perovskite, providing insights into intrinsic material properties beyond nanostructures.

Findings

Bright exciton fine structure splitting of ~200 μeV observed in bulk crystal

Splitting size indicates intrinsic material property, not quantum confinement effects

Results inform understanding of exciton behavior in perovskite nanocrystals

Abstract

Exciton fine structure splitting in semiconductors reflects the underlying symmetry of the crystal and quantum confinement. Since the latter factor strongly enhances the exchange interaction, most work has focused on nanostructures. Here, we report on the first observation of the bright exciton fine structure splitting in a bulk semiconductor crystal, where the impact of quantum confinement can be specifically excluded, giving access to the intrinsic properties of the material. Detailed investigation of the exciton photoluminescence and reflection spectra of a bulk methylammonium lead tribromide single crystal reveals a zero magnetic field splitting as large as $\sim 200\mu$eV. This result provides an important starting point for the discussion of the origin of the large bright exciton fine structure observed in perovskite nanocrystals.