Orbitronics: Light-induced Orbit Currents in Terahertz Emission Experiments

TL;DR

This paper demonstrates that femtosecond light pulses can generate orbit currents in Ni-based multilayers, which can be converted into charge currents and terahertz emission, advancing the field of orbitronics.

Contribution

It introduces the generation of light-induced orbit currents in Ni and Ni-based multilayers, a novel method in orbitronics research.

Findings

Orbit currents dominate light-induced spin currents in Ni systems.

Terahertz emission results from orbit current conversion into charge currents.

Time delay analysis reveals orbit carrier velocity and propagation.

Abstract

Orbitronics is based on the use of orbit currents as information carriers. Up to now, orbit currents were created from the conversion of charge or spin currents, and inversely, they could be converted back to charge or spin currents. Here we demonstrate that orbit 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 orbit currents by their conversion into charge currents and the resulting terahertz emission. We show that the orbit 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 of orbit carriers. Our finding of light-induced orbit currents and our observation of their conversion into charge currents opens new avenues in orbitronics, including the development of orbitronic terahertz devices.