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| Main Authors: | , , , , , , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2511.20268 |
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| _version_ | 1866910247102185472 |
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| author | Bork, Sophie Leven, Richard Wirsdörfer, Vincent Ferretti, Alessandro Rojas-Lopez, Rafael R. Benini, Mattia Janas, David Maximilian Parlak, Umut Brambilla, Alberto Scherbakov, Alexey V. Acharya, Swagata Cinchetti, Mirko |
| author_facet | Bork, Sophie Leven, Richard Wirsdörfer, Vincent Ferretti, Alessandro Rojas-Lopez, Rafael R. Benini, Mattia Janas, David Maximilian Parlak, Umut Brambilla, Alberto Scherbakov, Alexey V. Acharya, Swagata Cinchetti, Mirko |
| contents | Collective spin and lattice excitations in quantum materials span energy scales from GHz to THz, yet establishing a unified optical interface for these modes remains a central challenge. Here we show that excitonic resonances in the van der Waals antiferromagnet CrSBr provide a broadband optical interface for such excitations. Using femtosecond broadband transient reflectivity, we resolve coherent GHz magnon and THz phonon modes that modulate the dielectric response over a wide spectral range. Despite their distinct microscopic origin and frequency scales, both excitations give rise to the same emergent optical signature: a resonance at 1.46 eV that is absent in steady-state spectra and exhibits a characteristic π-phase inversion, identifying it as a discrete excitonic transition. We attribute this behaviour to boson-driven modulation of the dielectric response, which transiently transfers spectral weight from a nominally dark exciton into an observable channel without requiring a finite equilibrium oscillator strength. Supported by many-body calculations, we assign this feature to a higher-energy exciton with distinct momentum and orbital character and strongly suppressed optical matrix elements. These results establish excitonic resonances in van der Waals magnets as a platform for interfacing collective excitations across GHz, THz and optical frequency scales. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_20268 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Excitonic optical interface for GHz-THz collective excitations in a van der Waals magnet Bork, Sophie Leven, Richard Wirsdörfer, Vincent Ferretti, Alessandro Rojas-Lopez, Rafael R. Benini, Mattia Janas, David Maximilian Parlak, Umut Brambilla, Alberto Scherbakov, Alexey V. Acharya, Swagata Cinchetti, Mirko Materials Science Collective spin and lattice excitations in quantum materials span energy scales from GHz to THz, yet establishing a unified optical interface for these modes remains a central challenge. Here we show that excitonic resonances in the van der Waals antiferromagnet CrSBr provide a broadband optical interface for such excitations. Using femtosecond broadband transient reflectivity, we resolve coherent GHz magnon and THz phonon modes that modulate the dielectric response over a wide spectral range. Despite their distinct microscopic origin and frequency scales, both excitations give rise to the same emergent optical signature: a resonance at 1.46 eV that is absent in steady-state spectra and exhibits a characteristic π-phase inversion, identifying it as a discrete excitonic transition. We attribute this behaviour to boson-driven modulation of the dielectric response, which transiently transfers spectral weight from a nominally dark exciton into an observable channel without requiring a finite equilibrium oscillator strength. Supported by many-body calculations, we assign this feature to a higher-energy exciton with distinct momentum and orbital character and strongly suppressed optical matrix elements. These results establish excitonic resonances in van der Waals magnets as a platform for interfacing collective excitations across GHz, THz and optical frequency scales. |
| title | Excitonic optical interface for GHz-THz collective excitations in a van der Waals magnet |
| topic | Materials Science |
| url | https://arxiv.org/abs/2511.20268 |