Spin-to-charge-current conversion in altermagnetic candidate RuO$_2$ probed by terahertz emission spectroscopy

J. Jechumtál; O. Gueckstock; K. Jasenský; Z. Kašpar; K Olejník; M. Gaerner; G. Reiss; S. Moser; P. Kessler; G. De Luca; S. Ganguly; J. Santiso; D. Scheffler; J. Zázvorka; P. Kubaščík; H. Reichlova; E. Schmoranzerova; P. Němec; T. Jungwirth; P. Kužel; T. Kampfrath; L. Nádvorník

arXiv · 2508.11481

Spin-to-charge-current conversion in altermagnetic candidate RuO$_2$ probed by terahertz emission spectroscopy

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Abstract

Using the THz emission spectroscopy, we investigate ultrafast spin-to-charge current conversion in epitaxial thin films of the altermagnetic candidate RuO$_2$. We perform a quantitative analysis of competing effects that can contribute to the measured anisotropic THz emission. These include the anisotropic inverse spin splitter and spin Hall effects in RuO$_2$, the anisotropic conductivity of RuO$_2$, and the birefringence of the TiO$_2$ substrate. We observe that the leading contribution to the measured signals comes from the anisotropic inverse spin Hall effect, with an average spin-Hall angle of $2.4\times 10^{-3}$ at room temperature. In comparison, a possible contribution from the altermagnetic inverse spin-splitter effect is found to be approximately $2-4\times 10^{-4}$. Our work stresses the importance of carefully disentangling spin-dependent phenomena that can be generated by the unconventional altermagnetic order, from the effects of the relativistic spin-orbit coupling.

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J. Jechumtál, O. Gueckstock, K. Jasenský, Z. Kašpar, K Olejník, M. Gaerner, G. Reiss, S. Moser, P. Kessler, G. De Luca, S. Ganguly, J. Santiso, D. Scheffler, J. Zázvorka, P. Kubaščík, H. Reichlova, E. Schmoranzerova, P. Němec, T. Jungwirth, P. Kužel, T. Kampfrath, L. Nádvorník. 2025-08-15. Spin-to-charge-current conversion in altermagnetic candidate RuO$_2$ probed by terahertz emission spectroscopy. https://arxiv.org/abs/2508.11481

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