超短自旋电流脉冲注入半导体的自旋极化
Spin polarisation of ultrashort spin current pulses injected in semiconductors
摘要：
超短自旋电流脉冲在未来的超快自旋电子学中具有很大的信息载体潜力。它们呈现出极其压缩的时间分布的突出特性，这可以允许建立在前所未有的THz频率下运行的自旋电子学。然而，超短自旋脉冲仍然缺乏其他期望的特征。例如，空间分布更类似于溢出而不是空间压缩脉冲。此外，超短自旋电流脉冲只能在金属中传播很短的距离。超短自旋脉冲从金属铁磁体注入到半导体中，在那里它们必须被产生，作为第一步，通过允许激发的电子在几乎没有散射的介质中传播来克服这两个问题。然而，由于化学和结构稳定性等实际限制，设计用于注射的有效界面具有挑战性。因此，这项工作将注入的研究扩展到更广泛的界面，并分析不同的金属层和半导体如何影响超短脉冲的振幅，自旋极化和持续时间。这为选择有效的接口提供了指导方针，同样重要的是，实验测试的趋势。
英文摘要：
Ultrashort spin current pulses have a great potential of becoming the carriers of information in future ultrafast spintronics. They present the outstanding property of an extremely compressed time profile, which can allow for the building up of spintronics operating at the unprecedented THz frequencies. The ultrashort spin pulses, however still lack other desirable features. For instance the spatial profile resembles more that of a spill rather than that of a spatially compressed pulse. Moreover the ultrashort spin current pulses can travel only across small distances in metals. The injection of the ultrashort spin pulses from the metallic ferromagnet, where they have to be generated, into a semiconductor is proposed as the first step to overcome both issues by allowing the exited electrons to propagate in a medium with few scatterings. However designing efficient interfaces for the injection is challenging due to practical constraints like chemical and structural stability. This work therefore expands the study of injection to a broader range of interfaces, and analyses how different metallic layers and semiconductors influence the amplitude, the spin polarisation and duration of the ultrashort pulses. This provides guidelines for the selection of efficient interfaces and, equally importantly, experimentally testable trends.
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