在金属/非晶界面中形成具有高迁移率的新型二维电子气（2DEG）激发了关于这些2DEG的形成和新特性的持续辩论。在这里，我们报告了一个光学研究，基于红外光谱椭圆偏振法，金属和非晶半导体氧化物（Cu/Bi $_2$ O $_3$）接口，确认形成的2DEG与自旋轨道耦合（SOC）。在亚纳米薄层内用单轴对角介电张量模拟2DEG光学响应，其中其$x$和$z$分量线形在自由电子和类峰贡献中分辨，结果与理论预测非常相似[M. Xie等人，Phys. Rev. B $\bf{89}$，245417（2014）]中描述的方法，该方法包括在钙钛矿界面的法线方向上限制二维电子气。特别地，$z$组分的小但有限的导电特性提供了Cu/Bi $_2$ O $_3$系统中存在2DEG的明确特征。虽然原始组成材料不具有自旋轨道耦合（SOC），但由此产生的这种状态的界面杂化诱导电子不对称波函数。这项工作证明了在非晶晶体中检测2DEG，从而可以研究其具有挑战性的界面现象，如SOC和界面-体耦合，克服了几十年来阻碍非晶材料中2DEG理解的重要进展的实验障碍。
英文摘要：
The formation of novel two-dimensional electron gas (2DEG) with high mobility in metal/amorphous interfaces has motivated an ongoing debate regarding the formation and novel characteristics of these 2DEGs. Here we report an optical study, based on infrared spectroscopic ellipsometry, of nonmagnetic metal and amorphous semiconducting oxide (Cu/Bi$_2$O$_3$) interfaces that confirms the formation of a 2DEG with spin orbit coupling (SOC). The 2DEG optical response was simulated with a uniaxial diagonal dielectric tensor within a sub-nanometer thin layer, where its $x$ and $z$ components lineshapes resolved in both free-electron and peak-like contributions, resulted very similar to theoretical predictions [M. Xie et al., Phys. Rev. B $\bf{89}$, 245417 (2014)] of a two dimensional electron gas confined in the normal direction of a perovskite interface. In particular, the small but finite conducting character of the $z$ component provides a unambiguous signature of the presence of the 2DEG in the Cu/Bi$_2$O$_3$ system. Although the original constituent materials do not possess spin-orbit coupling (SOC), the resulting interfacial hybridization of such states induce electronic asymmetric wave functions. This work demonstrates the detection of 2DEG in amorphous crystals allowing to study its challenging interfacial phenomena such as SOC and interface-bulk coupling, overcoming an experimental impediment which has hold back for decades important advancements for the understanding of 2DEGs in amorphous materials.
Spin absorption at ferromagnetic-metal/platinum-oxide interface
通过测量电流感生铁磁共振，研究了自旋电流在铁磁金属/铂氧化物界面的吸收。自旋吸收由异质结构的磁阻尼来表征。我们表明，磁阻尼的Ni $_{81}$ Fe $_{19}$膜的明显增强，通过附加Pt氧化物上的Ni $_{81}$ Fe $_{19}$膜。通过在Ni $_{81}$ Fe $_{19}$和Pt氧化物层之间插入一层Cu层，阻尼增强消失。这些结果证明了Ni $_{81}$ Fe $_{19}$和Pt氧化物之间的直接接触对诱导相当大的界面自旋轨道耦合的重要作用。此外，Ni $_{81}$ Fe $_{19}$ /Pt-氧化物界面的自旋吸收参数与深入研究的具有强自旋-轨道耦合的异质结构（例如氧化物界面、拓扑绝缘体、具有Rashba自旋-轨道耦合的金属结）的自旋吸收参数相当。这一结果说明了强自旋轨道耦合在铁磁金属/铂氧化物界面，提供了一个重要的信息，定量了解自旋吸收和自旋电荷转换在铁磁金属/金属氧化物界面。
