Spin phase protection in interference of electron spin waves in lightly hydrogenated graphene
Spin phase protection in interference of electron spin waves in lightly hydrogenated graphene
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DOI：
10.1039/c6ra11648e
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发表时间：
2016-07
期刊：
影响因子：
3.9
通讯作者：
T. Kato;J. Kamijo;Taketomo Nakamura;C. Ohata;S. Katsumoto;J. Haruyama
中科院分区：
文献类型：
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作者：
T. Kato;J. Kamijo;Taketomo Nakamura;C. Ohata;S. Katsumoto;J. Haruyama
石墨烯中的电子自旋输运对外来原子和SiO2衬底的波纹极其敏感。事实上，所观察到的自旋扩散和弛豫长度（时间）小于理论上预期的，由于这一点，虽然一个大的自旋扩散长度最近已经实现了在SiC衬底上合成的石墨烯。因此，增强石墨烯/SiO2衬底的自旋相位相干性和自旋扩散（弛豫）长度是至关重要的，特别是对于未来的石墨烯自旋电子学。实现这一目标的途径之一是研究电子自旋波相位干涉现象（如弱局域化（WL））中的自旋相位及其与自旋轨道相互作用（SOI）的关系。然而，它们在石墨烯中的共存很难在实验上实现。在此，我们通过精确控制对在石墨烯上处理的包括氢原子的特定EB抗蚀剂的电子束（EB）照射量，实现了SiO2上石墨烯表面（≤ 0.1%）的极轻氢化。它允许WL和SOI共存。我们发现自旋相保护（抑制退相）的WL中的电子自旋波的温度和外部磁场的依赖性在石墨烯与氢化体积（NH）小至0.06%。作为起源，WL与Rashba型SOI的相关性，这可以通过面外对称性破缺，由于来自小NH的sp3键的形成而引入，进行了讨论。目前在轻度氢化的石墨烯中的发现对于石墨烯自旋电子学必须是有益的，这要求长的自旋扩散和相干长度。这将在石墨烯中实现一种可能的二维拓扑绝缘态。
Electron spin transport in graphene is extremely sensitive to foreign atoms and ripples of the SiO2 substrate. Indeed, the observed spin diffusion- and relaxation-length (time) were smaller than theoretically expected owing to this, although a large spin diffusion length has been recently realized in graphene synthesized on a SiC substrate. It is, thus, crucial to enhance the spin phase coherence and spin diffusion (relaxation) length of a graphene/SiO2 substrate particularly for future graphene spintronics. One of the approaches to realize this is the investigation of the spin phase in the phase interference phenomena of electron spin waves (such as weak localization (WL)) and its correlation with the spin–orbit-interaction (SOI). However, their coexistence in graphene is difficult to be realized experimentally. Here, we have realized the extremely light hydrogenation of a graphene surface (≪0.1%) on SiO2 by precisely controlling the amount of electron beam (EB) irradiation to a specific EB resist including hydrogen atoms, treated on graphene. It allows the coexistence of WL and the SOI. We find spin phase protection (suppression of dephasing) of the electron-spin-waves in the WL on temperature and external magnetic-field dependence in the graphenes with hydrogenation volumes (NH) as small as 0.06%. As an origin, correlation of the WL with a Rashba-type SOI, which can be introduced by out-of-plane symmetry breaking due to the formation of sp3 bonds derived from the small NH, is discussed. The present finding in lightly hydrogenated graphene must be beneficial for graphene spintronics, which requests a long spin diffusion- and coherence-length. It will realize a possible 2D-topological insulating state in graphene.