Observation of orbital pumping

Abstract: Harnessing spin and orbital angular momentum is a fundamental concept in condensed matter physics, materials science, and quantum-device applications. In particular, the search for new phenomena that generate a flow of spin angular momentum, a spin current, has led to the development of spintronics, advancing the understanding of angular momentum dynamics at the nanoscale. In contrast to this success, the generation and detection of orbital currents, the orbital counterpart of spin currents, remains a significant challenge. Here, we report the observation of orbital pumping, a phenomenon in which magnetization dynamics pumps an orbital current, a flow of orbital angular momentum. The orbital pumping is the orbital counterpart of the spin pumping, which is one of the most versatile and powerful mechanisms for spin-current generation. We show that the orbital pumping in Ni/Ti bilayers injects an orbital current into the Ti layer, which is detected through the inverse orbital Hall effect. Our findings provide a promising approach for generating orbital currents and pave the way for exploring the physics of orbital transport in solids.