Fingerprint of the inverse Rashba-Edelstein effect at heavy-metal/Cu interfaces

We report the direct observation of the fingerprint of the inverse Rashba-Edelstein effect (IREE) via investigations of the spin-to-charge conversion in Ta(Pt)/Cu and Cu/Ta(Pt) as a function of the heavy-metal thickness. The converted charge voltages have opposite signs for samples with reversed stacking orders in the ultrathin regime and have the same sign at higher thickness. The effect is demonstrated with two independent experimental approaches and supported by first-principles calculations. Our observations unambiguously demonstrate the existence of the IREE at heavy-metal/Cu interfaces and provide a framework for manipulating the spin-charge conversion via interface engineering.