Abstract
Orbital angular momentum has recently been demonstrated as a promising approach to manipulate magnetic order in spintronic devices with high efficiency. While the generation of orbital angular momentum is generally attributed to electron orbital hopping and hybridization, its experimental manifestations have often been discussed in an isotropic manner. In crystalline systems, however, orbital hybridization is inherently constrained by crystal symmetry, suggesting that symmetry can play a decisive role in shaping the anisotropy of orbital angular momentum-related responses. In this work, we report a crystal-symmetry-dependent orbital Rashba-Edelstein effect in a distinct epitaxially grown CuO thin film with four-fold crystal symmetry. A crystal-symmetry-dependent sign change of spin torque efficiency is observed in the CuO/ferromagnetic heterostructures, verified by second harmonic Hall measurement and current-induced perpendicular magnetization switching. The experimental results, together with the first-principles calculation, indicate the existence of a strong four-fold anisotropy of orbital Rashba-Edelstein effect in crystalline CuO, which is a direct manifestation of the crystal symmetry’s impact on the anisotropy of orbital angular momentum-related response. These findings establish crystal symmetry as a key factor governing the anisotropy of orbital angular momentum-related phenomena and provide a symmetry-based framework for orbitronic functionalities in advanced spintronic devices.
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References
Hirsch, J. E. Spin Hall Effect. Phys. Rev. Lett. 83, 1834–1837 (1999).
Jungwirth, T., Wunderlich, J. & Olejník, K. Spin Hall effect devices. Nat. Mater. 11, 382–390 (2012).
Manchon, A., Koo, H. C., Nitta, J., Frolov, S. M. & Duine, R. A. New perspectives for Rashba spin–orbit coupling. Nat. Mater. 14, 871–882 (2015).
Shanavas, K., Popović, Z. S. & Satpathy, S. Theoretical model for Rashba spin-orbit interaction in d electrons. Phys. Rev. B 90, 165108 (2014).
Miron, I. M. et al. Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection. Nature 476, 189–193 (2011).
Liu, L., Lee, O. J., Gudmundsen, T. J., Ralph, D. C. & Buhrman, R. A. Current-induced switching of perpendicularly magnetized magnetic layers using spin torque from the Spin Hall effect. Phys. Rev. Lett. 109, 096602 (2012).
Liu, L. et al. Symmetry-dependent field-free switching of perpendicular magnetization. Nat. Nanotechnol. 16, 277–282 (2021).
Liu, L. et al. Spin-torque switching with the Giant Spin Hall effect of Tantalum. Science 336, 555–558 (2012).
Manchon, A. et al. Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems. Rev. Mod. Phys. 91, 035004 (2019).
Choi, Y.-G. et al. Observation of the orbital Hall effect in a light metal Ti. Nature 619, 52–56 (2023).
Go, D. & Lee, H.-W. Orbital torque: Torque generation by orbital current injection. Phys. Rev. Res 2, 013177 (2020).
Jo, D., Go, D. & Lee, H.-W. Gigantic intrinsic orbital Hall effects in weakly spin-orbit coupled metals. Phys. Rev. B 98, 214405 (2018).
Go, D., Jo, D., Kim, C. & Lee, H.-W. Intrinsic Spin and Orbital Hall effects from orbital texture. Phys. Rev. Lett. 121, 086602 (2018).
Lee, D. et al. Orbital torque in magnetic bilayers. Nat. Commun. 12, 6710 (2021).
Ding, S. et al. Observation of the Orbital Rashba-Edelstein Magnetoresistance. Phys. Rev. Lett. 128, 067201 (2022).
Ding, S. et al. Harnessing orbital-to-spin conversion of interfacial orbital currents for efficient spin-orbit torques. Phys. Rev. Lett. 125, 177201 (2020).
Sala, G. & Gambardella, P. Giant orbital Hall effect and orbital-to-spin conversion in 3d, 5d, and 4f metallic heterostructures. Phys. Rev. Res 4, 033037 (2022).
Ding, S., Noël, P., Krishnaswamy, G. K. & Gambardella, P. Unidirectional orbital magnetoresistance in light-metal–ferromagnet bilayers. Phys. Rev. Res 4, L032041 (2022).
Cao, C. et al. Anomalous spin current anisotropy in a noncollinear antiferromagnet. Nat. Commun. 14, 5873 (2023).
Zhao, T. et al. Enhancement of out-of-plane spin–orbit torque by interfacial modification. Adv. Mater. 35, 2208954 (2023).
Zheng Z. et al. All-electrical perpendicular switching of chiral antiferromagnetic order. Nat. Mater. (2025).
Kontani, H., Tanaka, T., Hirashima, D., Yamada, K. & Inoue, J. Giant intrinsic spin and orbital Hall effects in Sr2MO4 (M= Ru, Rh, Mo). Phys. Rev. Lett. 100, 096601 (2008).
Oh, S. & Choi, H. J. Orbital angular momentum analysis for giant spin splitting in solids and nanostructures. Sci. Rep. 7, 2024 (2017).
Lyalin, I., Alikhah, S., Berritta, M., Oppeneer, P. M. & Kawakami, R. K. Magneto-optical detection of the orbital Hall effect in chromium. Phys. Rev. Lett. 131, 156702 (2023).
Wang, P. et al. Inverse orbital Hall effect and orbitronic terahertz emission observed in the materials with weak spin-orbit coupling. npj Quantum Mater. 8, 28 (2023).
Gupta, R. et al. Harnessing orbital Hall effect in spin-orbit torque MRAM. Nat. Commun. 16, 130 (2025).
Santos, E. et al. Exploring orbital-charge conversion mediated by interfaces with CuOx through spin-orbital pumping. Phys. Rev. B 109, 014420 (2024).
Zheng, Z. et al. Effective electrical manipulation of a topological antiferromagnet by orbital torques. Nat. Commun. 15, 745 (2024).
An, T. et al. Electrical manipulation of orbital current via oxygen migration in Ni81Fe19/CuOx/TaN heterostructure. Adv. Mater. 35, 2300858 (2023).
Kageyama, Y. et al. Spin-orbit torque manipulated by fine-tuning of oxygen-induced orbital hybridization. Sci. Adv. 5, eaax4278 (2019).
Kita, R., Hase, T., Sasaki, M., Morishita, T. & Tanaka, S. Epitaxial growth of CuO thin films by in situ oxidation of Cu thin films. J. Cryst. Growth 115, 752–757 (1991).
Yang, P., Liu, H., Chen, Z., Chen, L. & Wang, J. Unit-cell determination of epitaxial thin films based on reciprocal-space vectors by high-resolution X-ray diffractometry. J. Appl. Crystallogr. 47, 402–413 (2014).
Kang, M.-G. et al. Electric-field control of field-free spin-orbit torque switching via laterally modulated Rashba effect in Pt/Co/AlOx structures. Nat. Commun. 12, 7111 (2021).
Ren, L. et al. Efficient spin–orbit torque switching in a perpendicularly magnetized Heusler alloy MnPtGe single layer. ACS Nano 17, 6400–6409 (2023).
Heinemann, M., Eifert, B. & Heiliger, C. Band structure and phase stability of the copper oxides Cu2O, CuO, and Cu4O3. Phys. Rev. B 87, 115111 (2013).
El Hamdi, A. et al. Observation of the orbital inverse Rashba–Edelstein effect. Nat. Phys. 19, 1855–1860 (2023).
Acknowledgements
J.C. acknowledges financial support from the Singapore Ministry of Education MOE-T2EP50223-0006, Singapore National Research Foundation Investigatorship (Grant No. NRF-NRFI10−2024-0010). Science and Technology Project of Jiangsu Province (BZ2022056). I. B., H. L., and H.-W.L. were supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (RS-2024-00410027). Supercomputing resources, including technical support, were provided by the Supercomputing Center, Korea Institute of Science and Technology Information (Contract No. KSC-2024-CRE-0319). P.Y. is supported by Singapore Synchrotron Light Source (SSLS) via NUS Core Support C-380-003-003-001. The authors would like to acknowledge SSLS for accessing the facility necessary for conducting the research. The Laboratory is a National Research Infrastructure under the National Research Foundation (NRF), Singapore.
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J.S.C. and H.-W.L. supervised the project. R.X. and J.S.C. conceived the idea. R.X. deposited the films and fabricated the devices with assistance from T.Y.Z., Z.Y.Z., and S.S. R.X. and T.Y.Z. performed electrical transport measurements and analyzed the data with contributions from Z.Y.Z., Q.H.Z., L.X.J., R.X., and T.Y.Z. carried out structural analysis with assistance from P.Y. and X.J.Y. I.B. and H.L. performed the first-principles calculations under the supervision of H.-W.L. Z.R.X. conducted TEM measurements under the supervision of D.S.S. R.X., T.Y.Z., Z.Y.Z., and J.S.C. wrote the manuscript. All authors discussed the results and commented on the manuscript.
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Xiao, R., Zhao, T., Baek, I. et al. Crystal symmetry-dependent Orbital Rashba Edelstein effect in epitaxial CuO thin film. Nat Commun (2026). https://doi.org/10.1038/s41467-026-71018-6
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DOI: https://doi.org/10.1038/s41467-026-71018-6
