Spin swapping mediated by spin-orbital textures in centrosymmetric multiorbital materials

Abstract

Spin swapping converts a primary spin current into a secondary one by interchanging its flow and spin-polarization directions, attributed to spin-orbit scattering or spin-band splitting. Here we uncover a fundamentally distinct route to spin swapping arising from the orbital degree of freedom in the spin pumping to centrosymmetric multiorbital materials \textit{without spin-band splitting}. When the dynamical proximity ferromagnet injects a longitudinal spin current flowing normal to the interface, spin-orbit-entangled orbital textures redirect the injected spins into longitudinal and transverse orbital currents. Their subsequent conversion back to the spin sector generates transverse spin currents with propagation and polarization directions swapped relative to the primary spin current. The swapping efficiency achieves $50\%$ for Ge and Si. Governed by a fourth-rank tensor constrained by crystalline symmetry and without requiring spin-orbit scattering or inversion symmetry breaking, our finding reveals spin-orbital textures as hidden intermediate channels of spin swapping with unexplored material choices and functionalities.