Enhancement of exciton valley polarization in monolayer MoS2 induced by scattering
Enhancement of exciton valley polarization in monolayer MoS2 induced by scattering
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DOI：
10.1103/physrevb.104.l121408
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发表时间：
2021-09
影响因子：
3.7
通讯作者：
Yueh-Chun Wu;T. Taniguchi;Kenji Watanabe;Jun Yan
中科院分区：
文献类型：
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作者：
Yueh-Chun Wu;T. Taniguchi;Kenji Watanabe;Jun Yan
我们报道了单层二硫化钼中散射引起的谷极化增强。热激活和电荷掺杂引入散射，我们的样品表现出七倍和十二倍的改善分别。这种违反直觉的效果是由于激子动量的快速调制和伴随的局部交换相互作用场引起的谷赝自旋进动的中断，在时间尺度上比进动周期短得多。相反，谷相干性通过热激活散射而不是通过电荷掺杂诱导的散射得到改善。我们提出这是由于各向异性的赝自旋散射和推广的Maialle-Silva-Sham模型定量解释我们的实验结果。我们的工作表明，具有最小散射的更清洁的样品，例如那些仔细悬浮或由六方氮化硼保护的样品，不一定会导致良好的谷极化。良好控制的散射实际上可以提供用于改进谷电子器件的有趣方法。
We report on scattering induced valley polarization enhancement in monolayer molybdenum disulfide. With thermally activated and charge doping introduced scattering, our sample exhibits sevenand twelve-folds of improvements respectively. This counter-intuitive effect is attributed to disruptions to valley pseudospin precession caused by rapid modulation of exciton momentum and concomitant local exchange interaction field, at time scales much shorter than the precession period. In contrast, the valley coherence is improved by thermally activated scattering, but not by charge doping induced scattering. We propose that this is due to anisotropic pseudospin scattering and generalize the Maialle-Silva-Sham model to quantitatively explain our experimental results. Our work illustrates that cleaner samples with minimal scattering, such as those carefully suspended or protected by hexagonal boron nitride, do not necessarily lead to good valley polarization. Well-controlled scattering can in fact provide an interesting approach for improving valleytronic devices.