Effect of Cu Intercalation Layer on the Enhancement of Spin-to-Charge Conversion in Py/Cu/Bi 2 Se 3 .

The spin-to-charge conversion in Permalloy (Py)/Cu/Bi 2 Se 3 is tunable by changing the Cu layer thickness. The conversion rate was studied using the spin pumping technique. The inverse Edelstein effect (IEE) length λ IEE is found to increase up to ~2.7 nm when a 7 nm Cu layer is introduced. Interestingly, the maximized λ IEE is obtained when the effective spin-mixing conductance (and thus J s ) is decreased due to Cu insertion. The monotonic increase in λ IEE with decreasing J s suggests that the IEE relaxation time (τ) is enhanced due to the additional tunnelling barrier (Cu layer) that limits the interfacial transmission rate. The results demonstrate the importance of interface engineering in the magnetic heterostructure of Py/topological insulators (TIs), the key factor in optimizing spin-to-charge conversion efficiency.