Magnetically brightened dark electron-phonon bound states in a van der Waals antiferromagnet.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 35013277.
- Also identified by DOI 10.1038/s41467-021-27741-3 and PMC identifier 8748959.
- 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
In van der Waals (vdW) materials, strong coupling between different degrees of freedom can hybridize elementary excitations into bound states with mixed character<sup>1-3</sup>. Correctly identifying the nature and composition of these bound states is key to understanding their ground state properties and excitation spectra<sup>4,5</sup>. Here, we use ultrafast spectroscopy to reveal bound states of d-orbitals and phonons in 2D vdW antiferromagnet NiPS<sub>3</sub>. These bound states manifest themselves through equally spaced phonon replicas in frequency domain. These states are optically dark above the Néel temperature and become accessible with magnetic order. By launching this phonon and spectrally tracking its amplitude, we establish the electronic origin of bound states as localized d-d excitations. Our data directly yield electron-phonon coupling strength which exceeds the highest known value in 2D systems<sup>6</sup>. These results demonstrate NiPS<sub>3</sub> as a platform to study strong interactions between spins, orbitals and lattice, and open pathways to coherent control of 2D magnets.