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arXiv · 2512.08385

Chiral-phonon generation of orbital currents in light transition metals

Marc Rovirola·Júlia Òdena·Anna Castellví·Quim Badosa·Blai Casals·Adrián Gudín·Haripriya Madathil·Fernando Ajejas·Paolo Perna·Alberto Hernández-Mínguez·Joan Manel Hernández·Saül Vélez·Ferran Macià
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Abstract

Orbital angular momentum offers a new channel for information transport in a vast set of materials. Its coherent generation and detection remain, however, largely unexplored. Here, we demonstrate that chiral surface acoustic waves (SAWs) generate sizable orbital currents in light-metal/ferromagnet bilayers through both the acoustic orbital Hall effect and acoustic orbital pumping. Using symmetry analysis of SAW-driven voltages, we disentangle vorticity-sensitive orbital currents arising from lattice rotation in the non-magnetic layer from angular-momentum pumping from the ferromagnet. Strong signals are observed only in nickel/chromium and nickel/titanium, while nickel/aluminum and all cobalt-based bilayers show negligible responses, revealing the critical roles of orbital Hall conductivity, phonon-orbital coupling, and interfacial orbital transparency. Comparison with spin-torque ferromagnetic resonance and second-harmonic measurements -- where electrically driven orbital angular momentum are weaker -- demonstrates that phonon excitation generates orbital currents more efficiently. These results establish chiral SAWs as an effective route for orbitronic functionality and open pathways toward phonon-controlled orbital magnetism.

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Marc Rovirola, Júlia Òdena, Anna Castellví, Quim Badosa, Blai Casals, Adrián Gudín, Haripriya Madathil, Fernando Ajejas, Paolo Perna, Alberto Hernández-Mínguez, Joan Manel Hernández, Saül Vélez, Ferran Macià. 2025-12-09. Chiral-phonon generation of orbital currents in light transition metals. https://arxiv.org/abs/2512.08385

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