Nonlocal Electrical Detection of Reciprocal Orbital Edelstein Effect

Abstract Spin-Orbitronics leverages the spin and orbital degrees of freedom in solids for information processing1,2. The orbital Edelstein effect3–5 and orbital Hall effect1,6–9, where the charge current induces a nonequilibrium orbital angular momentum, offer a promising method to manipulate nanomagnets efficiently using light elements1,4–8. Despite extensive research, understanding the Onsager reciprocity of orbital transport—fundamentally rooted in the second law of thermodynamics and time-reversal symmetry—remains elusive. In this study, we experimentally test the Onsager reciprocity of orbital transport in an orbital Edelstein system4,10–12 by utilizing nonlocal measurements13–23. This method enables the precise identification of the chemical potential generated by orbital accumulation, avoiding the limitations associated with local measurements. Remarkably, we observe that the direct and inverse orbital-charge conversion processes produce identical electric voltages, confirming Onsager reciprocity in orbital transport. Additionally, we find that the orbital decay length, approximately 100 nm at room temperature, is independent of Cu thickness and decreases with lowering temperature, revealing a distinct contrast to spin transport behavior15. Our findings provide valuable insights into both the reciprocity of the charge-orbital interconversion and the nonlocal correlation of orbital degree of freedom, laying the ground for orbitronics devices with long-range interconnections.