论文标题
访问埋入电子状态的自旋结构
Accessing the spin structure of buried electronic states
论文作者
论文摘要
在旋转和角度分辨光发射光谱（SARPES）中，与光电电子的自旋方向一起测量了晶体固体中电子状态的能量摩孔分散。因此，该技术允许以旋转解析方式绘制材料的带结构。通过使用低能量光子进行SARPES测量，可以将技术的自旋灵敏度组合起来，由大型电子非弹性无弹性路径在这些动力学能量下提供，以直接访问埋入界面处的电子状态的自旋结构。在这里，我们通过使用SARPES来确定从拓扑绝缘子BI $ _2 $ _2 $ SE $ _3 $的光子胶片中发出的光电子的自旋极化，证明了这种能力。通过对膜中的预期自旋结构进行建模，我们表明观察到的复杂的自旋极化是来自拓扑 - 绝缘体膜的表面，散装和掩埋界面（底部表面）的自旋极化状态的集成自旋信号。因此，我们的结果使我们能够直接确定埋入的狄拉克接口状态的旋转纹理。这种能力对于在基于量子材料的或自旋的设备中发挥作用的自旋物理的最先进的光谱测量很有吸引力，在这些设备中，自旋偏振界面状态定义了设备的操作原理。
In spin- and angle-resolved photoemission spectroscopy (SARPES) the energy-momentum dispersion of electronic states in crystalline solids is measured along with the spin direction of the photoemitted electrons. The technique therefore allows for mapping out a material's band structure in a spin resolved fashion. By conducting SARPES measurements using low-energy photons, the spin sensitivity of the technique can be combined an increased bulk probe depth, provided by the large electron inelastic mean-free path at these kinetic energies, to directly access the spin structure of electronic states at buried interfaces. Here, we demonstrate this capability by using SARPES to determine the spin polarization of photoelectrons emitted from a 6-nm-thick film of the topological insulator Bi$_2$Se$_3$ using photons with an energy of 8.5 eV. By modelling the expected spin structure in the film, we show that the complex spin polarization that is observed is the integrated spin signal from spin-polarized states at the surface, bulk and buried interface (bottom surface) of the topological-insulator film. Our results therefore allows us to directly determine the spin texture of the buried Dirac interface state. This capability is highly attractive for state-of-the art spectroscopic measurements of the spin-physics at play in quantum-material based or spintronic devices where spin-polarized interface states define the operational principle of the devices.
