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.
@article{arxiv.2403.13897,
title = {Large Exciton Binding Energy in the Bulk van der Waals Magnet CrSBr},
author = {Shane Smolenski and Ming Wen and Qiuyang Li and Eoghan Downey and Adam Alfrey and Wenhao Liu and Aswin L. N. Kondusamy and Aaron Bostwick and Chris Jozwiak and Eli Rotenberg and Liuyan Zhao and Hui Deng and Bing Lv and Dominika Zgid and Emanuel Gull and Na Hyun Jo},
journal= {arXiv preprint arXiv:2403.13897},
year = {2025}
}