Distinct magneto-optical response of Frenkel and Wannier excitons in CrSBr.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41547858.
- Also identified by DOI 10.1038/s41467-026-68482-5 and PMC identifier 12916971.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Excitons in recently discovered two-dimensional magnetic semiconductors have emerged as a promising vehicle for optoelectronic and spin-photonic applications. To exploit novel possibilities magnetic degrees of freedom offer, insight into the interplay of magnetism, lattice and optical excitations becomes essential. We consider Chromium Sulphur Bromide, which has two kinds of excitons, X<sub>B</sub> at 1.8 eV and X<sub>A</sub> at 1.38 eV. Here we show, through a combination of many body perturbation theory and experiment, that X<sub>B</sub> is an order of magnitude more sensitive to magnetic and lattice perturbations than X<sub>A</sub>. We trace the difference to the latter being localised (Frenkel-like), while the former is delocalised (Wannier-Mott-like) - a coexistence rarely seen in two-dimensional materials. This finding is supported by the strong temperature and magnetic field (up to 85 Tesla) dependent shifts in optical response for X<sub>B</sub> (much smaller for X<sub>A</sub>), and we show it is related to X<sub>B</sub>'s tendency for delocalisation (in-plane and out-of-plane) and enhanced coupling with Ag phonon modes.