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arXiv · 2606.15128

Oxidation-induced ultrafast spin-to-orbital conversion at heavy-metal interfaces

Xiaoxue Zeng·Tianyi Zhang·Yaokai Niu·Qiye Wen·Zhiyong Zhong·Zhi-Min Liao·Peng Yan·Xiufeng Han·Lichuan Jin
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Abstract

Oxidation engineering provides a route to control orbital degrees of freedom, yet its role in spin-to-orbital conversion remains largely unexplored. Here, we report an efficient spin-to-orbital conversion mechanism driven by interfacial oxidation at heavy-metal interfaces. In W/Co/SiO2 heterostructures, terahertz emission exhibits a time delay that scales linearly with the W thickness, identifying orbital-current transport as the dominant origin. The emission amplitude is approximately three times larger than that of Co/Pt bilayers, indicating highly efficient conversion from spin to orbital angular momentum. Systematic variation of Co thickness, stoichiometry, and interface configuration reveals that the effect originates from oxidation of the W layer at the W/Co interface, which modulates the interfacial orbital texture. We further show that this mechanism is generic across different heavy metals and scales with their spin-orbit coupling strength. These results establish oxidation as an effective handle to engineer spin-to-orbital conversion and provide a general route toward orbitronic terahertz emitters.

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Xiaoxue Zeng, Tianyi Zhang, Yaokai Niu, Qiye Wen, Zhiyong Zhong, Zhi-Min Liao, Peng Yan, Xiufeng Han, Lichuan Jin. 2026-06-13. Oxidation-induced ultrafast spin-to-orbital conversion at heavy-metal interfaces. https://arxiv.org/abs/2606.15128

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