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arXiv 1507.07618cond-mat.mes-hall
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二维自旋模通过横向约束向螺旋态的转变

Transition of a 2D spin mode to a helical state by lateral confinement

P. Altmann, M. Kohda, C. Reichl, W. Wegscheider, G. Salis

摘要:

自旋-轨道相互作用(SOI)导致自旋在动量相关的自旋-轨道场附近发生旋进。在扩散二维(2D)电子气中,给定空间位置处的自旋取向取决于电子行进到该位置的轨迹。在向具有增加的横向约束的1D系统的过渡中,自旋取向变得越来越独立于轨迹。据预测,一个长寿命的螺旋自旋模式出现。在这里,我们可视化实验中的GaAs量子阱结构与各向同性SOI的这种转变。空间分辨的测量表明已经形成了非量化和非弹道通道的螺旋模式。我们发现一个自旋寿命的增强,这是非常符合理论预测。2D电子气的横向限制提供了一种易于实现的技术,用于在存在强SOI的情况下实现宽范围的材料系统的高自旋寿命。

英文摘要:

Spin-orbit interaction (SOI) leads to spin precession about a momentum-dependent spin-orbit field. In a diffusive two-dimensional (2D) electron gas, the spin orientation at a given spatial position depends on which trajectory the electron travels to that position. In the transition to a 1D system with increasing lateral confinement, the spin orientation becomes more and more independent on the trajectory. It is predicted that a long-lived helical spin mode emerges. Here we visualize this transition experimentally in a GaAs quantum-well structure with isotropic SOI. Spatially resolved measurements show the formation of a helical mode already for non-quantized and non-ballistic channels. We find a spin-lifetime enhancement that is in excellent agreement with theoretical predictions. Lateral confinement of a 2D electron gas provides an easy-to-implement technique for achieving high spin lifetimes in the presence of strong SOI for a wide range of material systems.

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