Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA.
National Institute of Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
Phys Rev Lett. 2018 Jan 26;120(4):046402. doi: 10.1103/PhysRevLett.120.046402.
We report the experimental observation of 2s exciton radiative emission from monolayer tungsten diselenide, enabled by hexagonal boron nitride protected high-quality samples. The 2s luminescence is highly robust and persists up to 150 K, offering a new quantum entity for manipulating the valley degree of freedom. Remarkably, the 2s exciton displays superior valley polarization and coherence than 1s under similar experimental conditions. This observation provides evidence that the Coulomb-exchange-interaction-driven valley-depolarization process, the Maialle-Silva-Sham mechanism, plays an important role in valley excitons of monolayer transition metal dichalcogenides.
我们报告了在六方氮化硼保护的高质量样品的作用下，从单层二硒化钨中观察到 2s 激子辐射发射的实验结果。2s 发光非常稳定，在 150K 下仍然存在，为操纵谷自由度提供了一种新的量子实体。值得注意的是，在相似的实验条件下，2s 激子的谷极化和相干性优于 1s 激子。这一观察结果表明，库仑交换相互作用驱动的谷去极化过程，即 Maialle-Silva-Sham 机制，在单层过渡金属二卤化物的谷激子中起着重要作用。
