Momentum-Dark Intervalley Exciton in Monolayer Tungsten Diselenide Brightened via Chiral Phonon
Momentum-Dark Intervalley Exciton in Monolayer Tungsten Diselenide Brightened via Chiral Phonon
复制标题
通过手性声子增亮单层二硒化钨中的动量暗谷间激子
DOI：
10.1021/acsnano.9b06682
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发表时间：
2019-12-01
期刊：
影响因子：
17.1
通讯作者：
Shi, Su-Fei
中科院分区：
文献类型：
--
作者：
Li, Zhipeng;Wang, Tianmeng;Shi, Su-Fei
反转对称破缺和3重旋转对称性赋予了单层过渡金属二硫属化物中强激子的谷自由度，这可以用于谷电子学应用。然而，激子的短寿命极大地限制了可能的应用。相反，暗激子可以是长寿命的，但不一定具有谷自由度。在这项工作中，我们报告的动量暗，谷间激子在单层WSe 2通过低温磁光致发光光谱的识别。同时，在布里渊区的角点（K点），通过发射手征声子使谷间激子变亮，并将声子的赝角动量传递给发射光子，从而保留谷信息.手征声子能量被确定为类似于23毫电子伏，基于实验提取的交换相互作用（类似于7毫电子伏），与理论预期的24.6毫电子伏非常一致。具有谷自由度的长寿命谷间激子为谷电子学增加了一个激发准粒子，而手征声子与谷间激子之间的耦合为谷自旋操纵提供了场所.
Inversion symmetry breaking and 3-fold rotation symmetry grant the valley degree of freedom to the robust exciton in monolayer transition-metal dichalco-genides, which can be exploited for valleytronics applications. However, the short lifetime of the exciton significantly constrains the possible applications. In contrast, the dark exciton could be long-lived but does not necessarily possess the valley degree of freedom. In this work, we report the identification of the momentum-dark, intervalley exciton in monolayer WSe2 through low-temperature magneto-photoluminescence spectra. Interest-ingly, the intervalley exciton is brightened through the emission of a chiral phonon at the corners of the Brillouin zone (K point), and the pseudoangular momentum of the phonon is transferred to the emitted photon to preserve the valley information. The chiral phonon energy is determined to be similar to 23 meV, based on the experimentally extracted exchange interaction (similar to 7 meV), in excellent agreement with the theoretical expectation of 24.6 meV. The long-lived intervalley exciton with valley degree of freedom adds an exciting quasiparticle for valleytronics, and the coupling between the chiral phonon and intervalley exciton furnishes a venue for valley spin manipulation.