Ultrafast control of coherent acoustic lattice dynamics in the transition metal dichalcogenide alloy WSSe
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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866910896635248640 |
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| author | Rey, Sergio I. Cross, Martin J. Welsch, Malte L. Schröder, Frederik Zhou, Binbin Stenger, Nicolas Jepsen, Peter U. Kelleher, Edmund J. R. |
| author_facet | Rey, Sergio I. Cross, Martin J. Welsch, Malte L. Schröder, Frederik Zhou, Binbin Stenger, Nicolas Jepsen, Peter U. Kelleher, Edmund J. R. |
| contents | Coherent acoustic phonons (CAPs)$-$propagating strain waves that can dynamically modify the structure and symmetry of a crystal$-$offer unique opportunities for controlling material properties. We investigate CAP generation in the Janus-like layered alloy tungsten sulfide selenide (WS$_x$Se$_{1-x}$, hereafter WSSe). Employing high-fluence photoexcitation at 400 nm combined with ultrafast transient reflection spectroscopy, we capture the carrier-lattice dynamics governed by a cascade of processes including rapid exciton formation, phonon recycling, and thermoelastic deformation. These phenomena precede the emergence of a robust CAP mode at 27 GHz. Notably, the CAP amplitude in WSSe substantially exceeds that observed in the symmetric parent crystals WS$_2$ and WSe$_2$, which we attribute to an enhanced coupling mediated by a built-in out-of-plane electric field arising from the inversion asymmetry of the WSSe alloy. Furthermore, the implementation of a tailored two-pulse excitation sequence enables optical control of the CAP, underscoring the potential of WSSe and related Janus-like layered alloys as versatile building blocks in optomechanical and nanoacoustic device applications. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_21520 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Ultrafast control of coherent acoustic lattice dynamics in the transition metal dichalcogenide alloy WSSe Rey, Sergio I. Cross, Martin J. Welsch, Malte L. Schröder, Frederik Zhou, Binbin Stenger, Nicolas Jepsen, Peter U. Kelleher, Edmund J. R. Materials Science Optics Coherent acoustic phonons (CAPs)$-$propagating strain waves that can dynamically modify the structure and symmetry of a crystal$-$offer unique opportunities for controlling material properties. We investigate CAP generation in the Janus-like layered alloy tungsten sulfide selenide (WS$_x$Se$_{1-x}$, hereafter WSSe). Employing high-fluence photoexcitation at 400 nm combined with ultrafast transient reflection spectroscopy, we capture the carrier-lattice dynamics governed by a cascade of processes including rapid exciton formation, phonon recycling, and thermoelastic deformation. These phenomena precede the emergence of a robust CAP mode at 27 GHz. Notably, the CAP amplitude in WSSe substantially exceeds that observed in the symmetric parent crystals WS$_2$ and WSe$_2$, which we attribute to an enhanced coupling mediated by a built-in out-of-plane electric field arising from the inversion asymmetry of the WSSe alloy. Furthermore, the implementation of a tailored two-pulse excitation sequence enables optical control of the CAP, underscoring the potential of WSSe and related Janus-like layered alloys as versatile building blocks in optomechanical and nanoacoustic device applications. |
| title | Ultrafast control of coherent acoustic lattice dynamics in the transition metal dichalcogenide alloy WSSe |
| topic | Materials Science Optics |
| url | https://arxiv.org/abs/2503.21520 |