Optically initialized robust valley-polarized holes in monolayer WSe2.
Optically initialized robust valley-polarized holes in monolayer WSe2.
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DOI：
10.1038/ncomms9963
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发表时间：
2015-11-25
影响因子：
16.6
通讯作者：
Chang WH
中科院分区：
文献类型：
--
作者：
Hsu WT;Chen YL;Chen CH;Liu PS;Hou TH;Li LJ;Chang WH
在下一代电子学和光电子学中，强大的谷极化是利用谷赝自旋携带信息的关键先决条件。虽然具有固有自旋-谷耦合的单层过渡金属二硫族化合物为开发这种谷电子器件提供了一个独特的平台，但预期的长寿命谷伪自旋尚未被观察到。本文证明了单层WSe2的鲁棒谷偏振空穴可以通过光泵浦初始化。利用时间分辨克尔旋转光谱，我们观察到一个长寿命的谷极化，在低温下的寿命接近1ns，这比trion复合寿命（~ 10 - 20ps）要长得多。长寿命的谷极化是由谷赝自旋从光载流子转移到特定谷中的驻留空穴引起的。空穴的光初始化谷赝自旋即使在室温下也保持稳定，这为实现基于过渡金属二硫族化合物的室温谷电子学提供了可能。利用电子器件中的谷极化以及电荷和自旋所需的长相关寿命尚未被观察到。在这里，作者展示了WSe2中长寿命的谷偏振空穴的光激发。
A robust valley polarization is a key prerequisite for exploiting valley pseudospin to carry information in next-generation electronics and optoelectronics. Although monolayer transition metal dichalcogenides with inherent spin–valley coupling offer a unique platform to develop such valleytronic devices, the anticipated long-lived valley pseudospin has not been observed yet. Here we demonstrate that robust valley-polarized holes in monolayer WSe2 can be initialized by optical pumping. Using time-resolved Kerr rotation spectroscopy, we observe a long-lived valley polarization for positive trion with a lifetime approaching 1 ns at low temperatures, which is much longer than the trion recombination lifetime (∼10–20 ps). The long-lived valley polarization arises from the transfer of valley pseudospin from photocarriers to resident holes in a specific valley. The optically initialized valley pseudospin of holes remains robust even at room temperature, which opens up the possibility to realize room-temperature valleytronics based on transition metal dichalcogenides. The long associated lifetimes required to exploit valley polarization in electronic devices, along with charge and spin, have yet to be observed. Here, the authors demonstrate the photoexcitation of long-lived valley-polarized holes in WSe2.