The orbital Edelstein effect and orbital Hall effect, where a charge current

induces a nonequilibrium orbital angular momentum, offer a promising

method for efficiently manipulating nanomagnets using light elements.

Despite extensive research, understanding the Onsager’s reciprocity of orbital

transport remains elusive. In this study, we experimentally demonstrate the

Onsager’s reciprocity of orbital transport in an orbital Edelstein system by

utilizing nonlocal measurements. This method enables the precise identification

of the chemical potential generated by orbital accumulation, avoiding the

limitations associated with local measurements. We observe that the direct

and inverse orbital-charge conversion processes produce identical electric

voltages, confirming Onsager’s reciprocity in orbital transport. Additionally,

we find that the orbital decay length, approximately 100nm at room temperature,

is independent of the Cu thickness and decreases with decreasing

temperature, revealing a distinct contrast to the spin transport behavior. Our

findings provide valuable insights into both the reciprocity of the chargeorbital

interconversion and the nonlocal correlation of orbital degree of

freedom, laying the ground for orbitronics devices with long-range

interconnections.

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