Spin Pumping in Transferred Topological Insulator on Ferrimagnetic Insulator and Metal/ Ferrimagnetic Insulator

Efficient spin-to-charge conversion is expected in topological insulators (TIs) due to the large spin-orbit coupling (SOC) and the spin-momentum locking in the surface state. However, obtaining high quality TI films directly grown on various substrates such as ferrimagnetic insulator of yttrium iron garnets (YIG) is challenging, especially for novel phenomena that demand sharp interfaces. In this work we performed thorough study on exfoliated Bi₂Se₃ films transferred on YIG and Ag/YIG films. We demonstrated that in-plane ordered triangular domains and excellent crystallinity attained in MBE growth of Bi₂Se₃ on sapphire were preserved after the transfer process, as confirmed by AFM, XRD, and ARPES. Ferromagnetic resonance on the transferred Bi₂Se₃/YIG did not display the substantially enhanced damping constant, as was found in Bi₂Se₃/YIG by direct film growth. Spin pumping measurement was employed to investigate the spin-charge conversion from inverse Rashba-Edelstein effect or inverse spin Hall effect in transferred Bi₂Se₃/YIG and transferred Bi₂Se₃/Ag/YIG with varying Ag thickness. Our transfer technique has circumvented the difficulties of growing high quality Bi₂Se₃ on various substrates, providing a new route to fabricate TI-based heterostructures.