Coexistence of ultra-long spin relaxation time and coherent charge transport in organic single-crystal semiconductors
Coexistence of ultra-long spin relaxation time and coherent charge transport in organic single-crystal semiconductors
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DOI：
10.1038/nphys4217
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发表时间：
2017-10-01
期刊：
影响因子：
19.6
通讯作者：
Takeya, Jun
中科院分区：
文献类型：
--
作者：
Tsurumi, Junto;Matsui, Hiroyuki;Takeya, Jun
尽管货车德瓦耳斯键很弱，但由于高度周期性的静电势，有机半导体晶体中可以发生相干电荷输运。由于有机材料中的自旋-轨道耦合通常较弱，因此预计会有强大的自旋输运，如果要将其用于自旋电子学应用，这是必不可少的。在这样的系统中，通过散射事件发生动量弛豫，这使得能够为带状电荷传输定义本征迁移率，其为>10 cm（2）V-1 s（-1）。相比之下，有相对较少的实验研究的内在自旋弛豫的有机带输运系统。在这里，我们证明了有机半导体中的本征自旋弛豫也是由散射事件引起的，其频率比动量弛豫低得多。磁输运测量和电子自旋共振谱一致地显示在宽的温度范围内的两个弛豫时间之间的线性关系，清楚地表明了Elliott-Yafet类型的自旋弛豫机制。毫秒级的超长自旋寿命和相干带状输运的共存，导致微米级的自旋扩散长度，构成了实现基于有机单晶的自旋电子器件的关键一步。
Coherent charge transport can occur in organic semiconductor crystals thanks to the highly periodic electrostatic potential-despite the weak van der Waals bonds. And as spin-orbit coupling is usually weak in organic materials, robust spin transport is expected, which is essential if they are to be exploited for spintronic applications. In such systems, momentum relaxation occurs via scattering events, which enables an intrinsic mobility to be defined for band-like charge transport, which is >10 cm(2) V-1 s(-1). In contrast, there are relatively few experimental studies of the intrinsic spin relaxation for organic band-transport systems. Here, we demonstrate that the intrinsic spin relaxation in organic semiconductors is also caused by scattering events, with much less frequency than the momentum relaxation. Magnetotransport measurements and electron spin resonance spectroscopy consistently show a linear relationship between the two relaxation times over a wide temperature range, clearly manifesting the Elliott-Yafet type of spin relaxation mechanism. The coexistence of an ultra-long spin lifetime of milliseconds and the coherent band-like transport, resulting in a micrometre-scale spin diffusion length, constitutes a key step towards realizing spintronic devices based on organic single crystals.