隧道势垒电自旋探测器巨自旋探测效率的来源
On the origin of the giant spin detection efficiency in tunnel barrier based electrical spin detector
摘要：
在主流半导体中将自旋信号有效地转换为电压是自旋电子学的重大挑战之一。该过程通常通过铁磁隧道势垒实现，其中发生非线性电传输。在这项工作中，我们表明，非线性可能会导致一个自旋-电荷转换效率大于10倍的自旋极化的隧道势垒时，后者是在偏置的几个mV。我们确定的基本机制，负责这种非常有效的自旋检测的隧道势垒变形和导带移位所造成的施加电压的变化。此外，我们推导了探测器自旋灵敏度$P_{\textrm{det}}(V)$的近似解析表达式。对不同的势垒形状进行的计算表明，这种增强是存在于氧化物势垒以及肖特基隧道势垒，即使占主导地位的机制与势垒类型不同。此外，尽管自旋信号在高温下降低，但它仍然优于线性模型预测的值。我们的研究结果揭示了电自旋探测实验的解释和理解，并开辟了优化自旋输运器件性能的新途径。
英文摘要：
Efficient conversion of a spin signal into an electric voltage in mainstream semiconductors is one of the grand challenges of spintronics. This process is commonly achieved via a ferromagnetic tunnel barrier where non-linear electric transport occurs. In this work, we demonstrate that non-linearity may lead to a spin-to-charge conversion efficiency larger than 10 times the spin polarization of the tunnel barrier when the latter is under bias of a few mV. We identify the underlying mechanisms responsible for this remarkably efficient spin detection as the tunnel barrier deformation and the conduction band shift resulting from a change of applied voltage. In addition, we derive an approximate analytical expression for the detector spin sensitivity $P_{\textrm{det}}(V)$. Calculations performed for different barrier shapes show that this enhancement is present in oxide barriers as well as in Schottky tunnel barriers even if the dominant mechanisms differs with the barrier type. Moreover, although the spin signal is reduced at high temperatures, it remains superior to the value predicted by the linear model. Our findings shed light into the interpretation and understanding of electrical spin detection experiments and open new paths to optimize the performance of spin transport devices.
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