Enhancement of spin to charge conversion efficiency at the topological surface state by inserting normal metal spacer layer in the topological insulator based heterostructure*

We report efficient spin to charge conversion (SCC) in the topological insulator (TI) based heterostructure (BiSbT e1.5Se1.5/Cu/N i80F e20) by using spin-pumping technique. The SCC, characterized by inverse Edelstein effect length (λIEE) in the TI material alters with the Copper (Cu) interlayer thickness. It offers a new degree of freedom to manipulate SCC efficiency at the topological surface state. The significant enhancement of the measured spin-pumping voltage and the linewidth of ferromagnetic resonance (FMR) absorption spectra due to the insertion of Cu layer at the interface of TI and ferromagnetic metal (FM) indicates a reduction in spin memory loss at the interface that resulted from the presence of exchange coupling between the surface state of TI and the local moments of ferromagnetic metal. The temperature dependence (from 8K to 300K) of the evaluated λIEE data for all the trilayer systems, TI/Cu/FM with different Cu thickness confirms the effect of exchange coupling between the TI and FM layer on the spin to charge conversion efficiency of the topological surface state.