▎ 摘　　要

We propose an approach to detect spin currents in an even zigzag graphene nanoribbon (ZR) junction, based on the peculiar intervalley selection rule in the ribbon when only zero-energy modes are involved in transport. Spatial spin separation arises from the bipolar property of the undoped ZR and opposite pseudoparities of electrons in the conduction and valence bands, and does not involve any magnetic field or spin orbit interaction. A measurable fully spin-polarized charge current or potential can thus be converted from either coherent or incoherent spin resources. Our findings may shed light on making spintronics devices based on graphene nanoribbons.