Spin relaxation and spin coherence in nonmagnetic metallic ultrathin films and nanowires.

在自旋电子学领域，有一种利用自旋极化电流通过非磁性材料传递信息的愿景。然而，在任何材料中，自旋电流的耗散都会导致自旋松弛和信息丢失。相应的自旋弛豫速率取决于内在和外在因素，如点缺陷、晶体表面、晶格振动等，这些因素通过自旋轨道耦合（SOC）的作用共同促成自旋翻转散射。我们的目标是理解和定量预测这些现象，特别关注通常用于实验自旋电子学设备的薄和超薄金属薄膜，以及纳米线，其中降维可以导致令人惊讶的新物理。我们希望了解自旋弛豫如何受到样品依赖的电子结构的影响，例如表面状态，基底上的散射或样品制备过程中出现的杂质。我们想比较点缺陷处的散射效应和声子的散射效应，看看艾略特-雅菲特类型的弛豫是否占主导地位，或者自旋退相干的Dyakonov- Perel机制是否也很重要。最后，考虑到自旋-霍尔效应中自旋-轨道耦合的重要性，我们想看看在强自旋-轨道耦合存在的情况下，降维是否能部分抑制自旋弛豫。

In the field of spintronics, there is a vision of information transfer by spin-polarized currents through non-magnetic materials. In any material, however, dissipation of spin currents leads to spin relaxation and loss of information. The corresponding spin relaxation rate depends on intrinsic and extrinsic factors, such as point defects, crystal surfaces, lattice vibrations, etc., which all together contribute to spin-flip scattering via the effect of spin-orbit coupling (SOC). We aim at an understanding and quantitative prediction of these phenomena, with special focus on thin and ultra-thin metallic films that are commonly used in experimental spintronics devices, but also in nanowires where the reduced dimensionality can lead to surprising new physics. We wish to understand how spin relaxation is affected by the sample-dependent electronic structure, such as surface states, scattering at the substrate, or impurities that occur during sample preparation. We want to compare the effect of scattering at point defects to that of phonons, and to see if the Elliott-Yafet type of relaxation is dominant, or if the Dyakonov- Perel mechanism for spin decoherence can be also important. Finally we want to see if the reduced dimensionality can partly suppress spin relaxation even in the presence of strong spin-orbit coupling, in view of the importance of the latter for the spin-Hall effect.