Clear variation of spin splitting by changing electron distribution at non-magnetic metal/Bi2O3 interfaces

TL;DR

This study demonstrates that the spin splitting at non-magnetic metal/Bi2O3 interfaces can be significantly modulated by altering electron distribution, providing a new approach to control spin-to-charge conversion efficiency.

Contribution

The paper reveals how changing electron distribution at NM/Bi2O3 interfaces affects spin splitting, supported by experimental and first-principles calculations, offering a design principle for spintronic interfaces.

Findings

Large modulation of spin-to-charge conversion coefficient observed.

Sign change in conversion coefficient correlates with spin splitting variation.

Electron distribution near the interface is key to tuning spin splitting.

Abstract

Large spin splitting at Rashba interface, giving rise to strong spin-momentum locking, is essential for efficient spin-to-charge conversion. Recently, a Cu/Bismuth oxide (Bi2O3) interface has been found to exhibit an efficient spin-to-charge conversion similar to a Ag/Bi interface with large Rashba spin splitting. However, the guiding principle of designing the metal/oxide interface for the efficient conversion has not been clarified yet. Here we report strong non-magnetic (NM) material dependence of spin splitting at NM/Bi2O3 interfaces. We employed spin pumping technique to inject spin current into the interface and evaluated the magnitude of interfacial spin-to-charge conversion. We observed large modulation and sign change in conversion coefficient which corresponds to the variation of spin splitting. Our experimental results together with first-principles calculations indicate that such large variation is caused by material dependent electron distribution near the interface. The results suggest that control of interfacial electron distribution by tuning the difference in work function across the interface may be an effective way to tune the magnitude and sign of spin-to-charge conversion and Rashba parameter at interface.