Spin manipulation in semiconductor spin devices

这个项目的主要目标是演示通过电操作铁磁源和漏极触点之间的沟道中的自旋来控制横向半导体器件的电阻。这将构成1990年设想的达塔-达斯自旋场效应晶体管(SFET)概念的完全实现。在我们以前的工作中，我们已经实现了sFET的单一构件，即我们已经展示了非常有效的电子自旋注入到半导体二维电子气(2DEG)中，并且我们已经证明在这种器件中可以观察到高达80%的磁阻信号。因此，我们手头有充分实现达塔-达斯概念的所有要素。为此，我们计划重点关注两个主题。首先，我们将探索准一维(1D)沟道中的电自旋注入和自旋输运。这种通道虽然只有一种传输模式，但在最初的DATA-DAS提案中被引用。我们的设备构成了一个完美的试验台，用于研究在准一维通道中电注入面内自旋时对Dyakonov-Perel自旋弛豫的预期抑制。以前已经用光学方法对离面自旋进行了研究。其次，我们将直接讨论sFET的关键功能，即通过自旋轨道耦合(SOC)对横向局域器件中的自旋进动进行电控制，并在源极和漏极之间流动自旋极化电流。除了Datta和Das提出的原始几何结构外，我们还计划探索利用一维通道中的横向受限产生的横向自旋轨道耦合来诱导和控制自旋进动的可能性。

The main goal of this project is to demonstrate control of the resistance of a lateral semiconductor device by electrical manipulation of the spins in the channel between ferromagnetic source and drain contacts. This will constitute then a full realization of the concept of Datta-Das spin field effect transistor (sFET), envisioned in 1990. In our previous work, we have realized single building blocks of the sFET, namely we have shown very efficient electrical spin injection into a semiconductor two-dimensional electron gas (2DEG) and we have shown that high magnetoresistance signals up to 80% can be observed in such devices. We have therefore all ingredients at hand to pursue the full realization of the Datta-Das concept. To this end, we plan to focus on two topics. Firstly, we are going to explore electrical spin injection and spin transport in quasi one-dimensional (1D) channels. Such a channel, although with only one transport mode, was invoked in the original Datta-Das proposal. Our devices constitute a perfect test bed to investigate the expected suppression of Dyakonov-Perel spin relaxation in quasi 1D channels, for electrically injected in-plane spins. This has been studied before for out-of-plane spins using optical methods. Secondly, we are going to directly address the crucial functionality of the sFET, i.e., electrical control of the spin precession via spin orbit coupling (SOC), in lateral local devices, with a spin-polarized current flowing between source and drain contacts. Apart from the original geometry proposed by Datta and Das, with a metal gate on top of the channel, we plan to explore here also the possibility of using lateral spin orbit coupling, originating from the lateral confinement in 1D channels, to induce and control spin precession.