Orbital current, defined as the orbital character of Bloch states in solids, can travel with larger coherence length through a broader range of materials than its spin counterpart, facilitating a robust, higher density and energy efficient information transmission. Hence, active control of orbital transport plays a pivotal role in the progress of the evolving field of quantum information technology. Unlike spin angular momentum, orbital angular momentum couples to phonon angular momentum efficiently via orbital-crystal momentum (L-k) coupling, allowing us to control orbital transport through crystal field potential mediated angular momentum transfer. Here, leveraging the orbital dependant efficient L-k coupling, we have experimentally demonstrated the active control of orbital current velocity in Ni/Pt heterostructure. We observe terahertz emission from Ni/Pt heterostructure via long-range ballistic orbital transport, as evidenced by the delay, and chirping in the emitted THz pulse correlating with increased Pt thickness. Additionally, we also have identified a critical energy density required to overcome collisions in orbital transport, enabling a swifter flow of orbital current. Femtosecond light driven active control of the ballistic orbital transport lays the foundation for the development of dynamic optorbitronics for transmitting information over extended distance. The authors observe THz emission from Ni/Pt heterostructure due to long-range ballistic orbital transport. The velocity of orbital current can be optically tuned by laser fluence, opening the avenue for future optorbitronic devices.

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Nature

Researchers have demonstrated the active control of orbital current velocity in a Ni/Pt heterostructure through the use of femtosecond laser pulses. They observed terahertz emission from the heterostructure, indicating long-range ballistic orbital transport. The researchers also identified a critical energy density required to overcome collisions, enabling faster orbital current flow. This work lays the foundation for the development of dynamic optorbitronics and has potential applications in quantum information technology.

Active ballistic orbital transport in Ni/Pt heterostructure