Topological insulator (TI) based heterostructure is a prospective candidate for ultrahigh spin-to-charge conversion efficiency due to its unique surface states. We investigate the spin-to-charge conversion in (Bi,Sb)₂Te₃ (BST)/CoFeB, BST/Ru/CoFeB, and BST/Ti/CoFeB by spin pumping measurement. We find that the inverse Edelstein effect length (λ_IEE) increases by 60% with a Ru insertion while remains constant with a Ti insertion. This can be potentially explained by the protection of BST surface states due to the high electronegativity of Ru. Such enhancement is independent of the insertion layer thickness once the thickness of Ru is larger than 0.5 nm, and this result suggests that λ_IEE is very sensitive to the TI interface. In addition, an effectively perpendicular magnetic anisotropy field and additional magnetic damping are observed in the BST/CoFeB sample, which comes from the interfacial spin–orbit coupling between the BST and the CoFeB. Our work provides a method to enhance λ_IEE and is useful for the understanding of charge-to-spin conversion in TI-based systems.

中文翻译：

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通过界面工程提高拓扑绝缘体的自旋电荷转换效率

由于其独特的表面状态，基于拓扑绝缘体 (TI) 的异质结构是超高自旋电荷转换效率的潜在候选者。我们通过自旋泵浦测量研究了 (Bi,Sb) ₂ Te ₃ (BST)/CoFeB、BST/Ru/CoFeB 和 BST/Ti/CoFeB 中的自旋电荷转换。我们发现反 Edelstein 效应长度 ( λ _IEE ) 在插入 Ru 时增加了 60%，而在插入 Ti 时保持不变。由于 Ru 的高电负性，这可以通过保护 BST 表面状态来潜在地解释。一旦 Ru 的厚度大于 0.5 nm，这种增强与插入层厚度无关，该结果表明λ _IEE对 TI 接口非常敏感。此外，在 BST/CoFeB 样品中观察到有效垂直的磁各向异性场和额外的磁阻尼，这来自 BST 和 CoFeB 之间的界面自旋轨道耦合。我们的工作提供了一种增强λ _IEE的方法，有助于理解基于 TI 的系统中的电荷自旋转换。