Large Exciton Binding Energy in the Bulk van der Waals Magnet CrSBr

TL;DR

This study reveals an exceptionally large exciton binding energy in bulk CrSBr, driven by anisotropy and tunable via electric fields, advancing understanding of excitons in bulk van der Waals materials.

Contribution

It demonstrates that anisotropy in bulk CrSBr significantly enhances exciton binding energy, supported by spectroscopic and ab-initio calculations, and shows electric field tunability.

Findings

Large exciton binding energy observed in bulk CrSBr

Anisotropy amplifies exciton stability in bulk systems

Electric field enables tunable optical properties

Abstract

Excitons, bound electron-hole pairs, influence the optical properties in strongly interacting solid state systems. Excitons and their associated many-body physics are typically most stable and pronounced in monolayer materials. Bulk systems with large exciton binding energies, on the other hand, are rare and the mechanisms driving their stability are still relatively unexplored. Here, we report an exceptionally large exciton binding energy in single crystals of the bulk van der Waals antiferromagnet CrSBr. Utilizing state-of-the-art angle-resolved photoemission spectroscopy and self-consistent ab-initio GW calculations, we present direct spectroscopic evidence that robust electronic and structural anisotropy can significantly amplify the exciton binding energy within bulk crystals. Furthermore, the application of a vertical electric field enables broad tunability of the optical and electronic properties. Our results indicate that CrSBr is a promising material for the study of the role of anisotropy in strongly interacting bulk systems and for the development of exciton-based optoelectronics.