Orbitronics: light-induced orbital currents in Ni studied by terahertz emission experiments

• Published in: Nature communications Vol. 15; no. 1; pp. 2043 - 7
• Main Authors: Xu, Yong, Zhang, Fan, Fert, Albert, Jaffres, Henri-Yves, Liu, Yongshan, Xu, Renyou, Jiang, Yuhao, Cheng, Houyi, Zhao, Weisheng
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.03.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 140/125; 147/3; 639/301/1019/584; 639/301/357/997; 639/766/119/1001; Angular momentum; Copper; Current carriers; Electromagnetism; Electrons; Emission analysis; Emissions; Heavy metals; Heterostructures; Humanities and Social Sciences; Light; multidisciplinary; Multilayers; Nickel; Physics; Propagation velocity; Science; Science (multidisciplinary); Spin-orbit interactions; Timing
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-46405-6

Orbitronics is based on the use of orbital currents as information carriers. Orbital currents can be generated from the conversion of charge or spin currents, and inversely, they could be converted back to charge or spin currents. Here we demonstrate that orbital currents can also be generated by femtosecond light pulses on Ni. In multilayers associating Ni with oxides and nonmagnetic metals such as Cu, we detect the orbital currents by their conversion into charge currents and the resulting terahertz emission. We show that the orbital currents extraordinarily predominate the light-induced spin currents in Ni-based systems, whereas only spin currents can be detected with CoFeB-based systems. In addition, the analysis of the time delays of the terahertz pulses leads to relevant information on the velocity and propagation length of orbital carriers. Our finding of light-induced orbital currents and our observation of their conversion into charge currents opens new avenues in orbitronics, including the development of orbitronic terahertz devices. Several recent works have highlighted the importance of the orbital currents in transferring angular momentum within materials. In combination with spin-orbit coupling, such orbital currents can be used to alter the magnetization of a material. Herein, the authors demonstrate the inverse effect, showing orbital current driven terahertz emission in Nickel based heterostructures.