Abstract Considering the demand for long spin communication distance in spintronics, graphene presents micrometer spin relaxation length at room temperature, making it one of the most promising two dimensional spintronic materials. However, achieving efficient spin injection (including pure spin current and spin polarized current) by reducing the spin dependent scattering between graphene and other materials like contact is still a core challenge. Here, we propose a novel approach to generate spin current in zigzag graphene nanoribbon (ZGNR) via photogalvanic (or photovoltaic) effect (PGE) from atomic first principle calculations. By designing ZGNR based device with spatial inversion symmetry, we find that the PGE induced pure spin current can be hiddenly generated without accompanying charge current. Furthermore, through applying a dual gate in the system, the generated pure spin current can be controlled when dual gate voltages have the opposite signs. Interestingly, when the signs of dual gate voltages are the same, the pure spin current can turn into the fully spin polarized current. More importantly, the generated spin current via PGE is independent of photon polarization and incident angles. Our investigations demonstrate ZGNR’s great potential application in noninvasive spin injection of the graphene based spintronic device.

中文翻译：

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锯齿形石墨烯纳米带中栅极可控光学自旋电流的产生

摘要 考虑到自旋电子学对长自旋通信距离的需求，石墨烯在室温下呈现微米级的自旋弛豫长度，使其成为最有前途的二维自旋电子材料之一。然而，通过减少石墨烯和其他材料（如接触）之间的自旋相关散射来实现有效的自旋注入（包括纯自旋电流和自旋极化电流）仍然是一个核心挑战。在这里，我们提出了一种新方法，通过原子第一原理计算的光电流（或光伏）效应（PGE）在锯齿形石墨烯纳米带（ZGNR）中产生自旋电流。通过设计具有空间反转对称性的基于 ZGNR 的器件，我们发现 PGE 感应的纯自旋电流可以在没有伴随充电电流的情况下隐藏地产生。此外，通过在系统中应用双栅极，当双栅极电压具有相反符号时，可以控制产生的纯自旋电流。有趣的是，当双栅极电压的符号相同时，纯自旋电流可以变成完全自旋极化电流。更重要的是，通过 PGE 产生的自旋电流与光子极化和入射角无关。我们的研究证明了 ZGNR 在基于石墨烯的自旋电子器件的无创自旋注入中的巨大潜在应用。通过 PGE 产生的自旋电流与光子极化和入射角无关。我们的研究证明了 ZGNR 在基于石墨烯的自旋电子器件的无创自旋注入中的巨大潜在应用。通过 PGE 产生的自旋电流与光子极化和入射角无关。我们的研究证明了 ZGNR 在基于石墨烯的自旋电子器件的无创自旋注入中的巨大潜在应用。