AI 中文总结
该研究探究垂直磁化拓扑绝缘体-磁性多层异质结的温度依赖自旋轨道转矩，发现含Bi₂Se₃的异质结转矩显著增强，TI衍生的自旋动量锁定电流主导大阻尼类转矩，且受界面结构和缓冲层厚度影响。
AI 中文摘要
我们报道了对拓扑绝缘体（TI）外延层上方生长的垂直磁化金属多层膜构成的异质结中自旋轨道转矩（SOT）产生的全面温度依赖研究。温度依赖的二次谐波霍尔测量揭示了所研究异质结中自旋轨道转矩幅度的不同趋势。包含Bi₂Se₃的样品在15 K时的转矩达到约12 mT/(10¹² A m⁻²)，约为不含拓扑层的多层膜的5倍。带有2 nm厚Ta缓冲层的多层膜结构表现出最强的增强，且在低温下显著增加，突出了拓扑表面态产生的高效自旋电流。相比之下，带有10 nm厚Ta间隔层的样品转矩效率降低，与自旋通过缓冲层传输的部分衰减一致。不含Bi₂Se₃但包含两种重金属（Ta和Pt）的系统，尽管存在常规自旋霍尔源，产生的转矩仍显著更小，约为2.5 mT/(10¹² A m⁻²)。这些观察结果强调了TI衍生的自旋动量锁定电流在驱动大阻尼类转矩中的主导作用，以及其对界面结构和缓冲层厚度的敏感性。
英文摘要
We report a comprehensive temperature-dependent investigation of spin-orbit torque (SOT) generation in heterostructures comprising a perpendicularly magnetized metallic multilayer grown on top of a topological insulator (TI) epilayer. Temperature-dependent second-harmonic Hall measurements reveal distinct trends in the magnitude of the spin-orbit torque across the studied heterostructures. Samples incorporating Bi2Se3 exhibit torques reaching approximately 12 mT/(10^12 A m^-2) at 15 K, around 5 times larger than those in a multilayer without the topological layer. The structure with a thin 2-nm Ta buffer for the multilayer shows the strongest enhancement and a pronounced increase at low temperatures, highlighting efficient spin-current generation from the topological surface states. In contrast, the sample with a 10 nm-thick Ta spacer exhibits reduced torque efficiency, consistent with partial attenuation of spin transmission through the buffer. Systems lacking Bi2Se3 but containing two heavy metals (Ta and Pt) yield significantly smaller torques, around 2.5 mT/(10^12 A m^-2), despite the presence of conventional spin Hall sources. These observations underscore the dominant role of TI-derived spin-momentum-locked currents in driving large damping-like torques and their sensitivity to interfacial structure and buffer-layer thickness.
