Colossal enhancement of spin-orbit coupling in weakly hydrogenated graphene
Colossal enhancement of spin-orbit coupling in weakly hydrogenated graphene
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DOI：
10.1038/nphys2576
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发表时间：
2013-05-01
期刊：
影响因子：
19.6
通讯作者：
Oezyilmaz, Barbaros
中科院分区：
文献类型：
--
作者：
Balakrishnan, Jayakumar;Koon, Gavin Kok Wai;Oezyilmaz, Barbaros
石墨烯极小的自旋轨道（SO）相互作用(1)使得拓扑/量子自旋霍尔态（2,3）和自旋霍尔效应(4)（SHE）等许多有趣的现象几乎不可能实现。最近，有人预测（1,5-7），石墨烯中引入的附原子将通过sp(2)键转化为sp(3)键来增强SO相互作用。然而，在不产生电子定位（Anderson）的情况下，在引入合原子的同时保持石墨烯的金属性(8)，在实验上是具有挑战性的。在这里，我们证明了少量共价键氢原子的可控添加足以诱导SO相互作用的三个数量级的巨大增强。这导致在室温下零外部磁场的SHE，非局部自旋信号高达100欧米茄；数量级大于金属(9)。非局域SHE进一步由Larmor自旋进动测量直接证实。从这一点和非局部信号的长度依赖性中，我们提取了类似于1 μ m的自旋弛豫长度，类似于90 ps的自旋弛豫时间和2.5 meV的SO强度。
Graphene's extremely small intrinsic spin-orbit (SO) interaction(1) makes the realization of many interesting phenomena such as topological/quantum spin Hall states(2,3) and the spin Hall effect(4) (SHE) practically impossible. Recently, it was predicted(1,5-7) that the introduction of adatoms in graphene would enhance the SO interaction by the conversion of sp(2) to sp(3) bonds. However, introducing adatoms and yet keeping graphene metallic, that is, without creating electronic (Anderson) localization(8), is experimentally challenging. Here, we show that the controlled addition of small amounts of covalently bonded hydrogen atoms is sufficient to induce a colossal enhancement of the SO interaction by three orders of magnitude. This results in a SHE at zero external magnetic fields at room temperature, with non-local spin signals up to 100 Omega; orders of magnitude larger than in metals(9). The non-local SHE is, further, directly confirmed by Larmor spin-precession measurements. From this and the length dependence of the non-local signal we extract a spin relaxation length of similar to 1 mu m, a spin relaxation time of similar to 90 ps and a SO strength of 2.5 meV.