Silicon's weak intrinsic spin-orbit coupling and centrosymmetric crystal structure are a critical bottleneck to the development of Si spintronics, because they lead to an insignificant spin Hall effect (spin current generation) and inverse spin Hall effect (spin current detection). Here, we undertake current, magnetic field, crystallography dependent magnetoresistance, and magnetothermal transport measurements to study the spin transport behavior in freestanding Si thin films. We observe a large spin Hall magnetoresistance in both $p\text{−}\mathrm{Si}$ and $n\text{−}\mathrm{Si}$ at room temperature and it is an order of magnitude larger than that of Pt. One explanation of the unexpectedly large and efficient spin Hall effect is spin-phonon coupling instead of spin-orbit coupling. The macroscopic origin of the spin-phonon coupling can be large strain gradients that can exist in the freestanding Si films. This discovery in a light, earth abundant and centrosymmetric material opens a new path of strain engineering to achieve spin dependent properties in technologically highly developed materials.

中文翻译：

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室温下Si中的大自旋霍尔效应

硅的弱固有自旋轨道耦合和中心对称晶体结构是Si自旋电子学发展的关键瓶颈，因为它们导致微不足道的自旋霍尔效应（自旋电流产生）和逆自旋霍尔效应（自旋电流检测）。在这里，我们进行电流，磁场，晶体学相关的磁阻和磁热输运测量，以研究独立式Si薄膜中的自旋输运行为。我们观察到两个自旋霍尔磁阻$p\text{-}硅$ 和 $ñ\text{-}硅$在室温下，它比Pt大一个数量级。对自旋霍尔效应出乎意料的大而有效的解释是自旋声子耦合而不是自旋轨道耦合。自旋声子耦合的宏观起源可以是独立的Si膜中可能存在的大应变梯度。这种在轻质，地球丰富且中心对称的材料中的发现打开了应变工程的新途径，以在技术高度发达的材料中实现自旋相关的特性。