Ultrafast Exciton Dynamics in the Atomically Thin van der Waals Magnet CrSBr

Research output: Contribution to journalResearch articleContributedpeer-review



Among atomically thin semiconductors, CrSBr stands out as both its bulk and monolayer forms host tightly bound, quasi-one-dimensional excitons in a magnetic environment. Despite its pivotal importance for solid-state research, the exciton lifetime has remained unknown. While terahertz polarization probing can directly trace all excitons, independently of interband selection rules, the corresponding large far-field foci substantially exceed the lateral sample dimensions. Here, we combine terahertz polarization spectroscopy with near-field microscopy to reveal a femtosecond decay of paramagnetic excitons in a monolayer of CrSBr, which is 30 times shorter than the bulk lifetime. We unveil low-energy fingerprints of bound and unbound electron-hole pairs in bulk CrSBr and extract the nonequilibrium dielectric function of the monolayer in a model-free manner. Our results demonstrate the first direct access to the ultrafast dielectric response of quasi-one-dimensional excitons in CrSBr, potentially advancing the development of quantum devices based on ultrathin van der Waals magnets.


Original languageEnglish
Pages (from-to)4101-4107
Number of pages7
JournalNano letters
Issue number14
Publication statusPublished - 10 Apr 2024

External IDs

PubMed 38507732



  • anisotropic excitons, atomically thin solids, femtosecond near-field microscopy, terahertz, ultrafast dynamics, van der Waals magnets