Wu Yueh-Chun, Taniguchi Takashi, Watanabe Kenji, Yan Jun
Department of Physics, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States.
International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.
ACS Nano. 2023 Aug 22;17(16):15641-15647. doi: 10.1021/acsnano.3c02737. Epub 2023 Aug 1.
Monolayer transition metal dichalcogenide semiconductors are promising valleytronic materials. Among various quasi-particle excitations hosted by the system, the valley polarized holes are particularly interesting due to their long valley lifetime preserved by the large spin-orbit splitting and spin-valley locking in the valence band. Here we report that in the absence of any magnetic field a surprising valley splitting of exciton polarons can be induced by such valley polarized holes in monolayer WSe. The size of the splitting is comparable to that of the Zeeman effect in a magnetic field as high as 7 T and offers a quantitative approach to extract the hole density imbalance between the two valleys. We find that the density difference can easily achieve more than 10 per cm, and it is tunable by gate voltage as well as optical excitation power. Our study highlights the response of exciton polarons to optical pumping and advances understanding of valley dependent phenomena in monolayer transition metal dichalcogenide.
单层过渡金属二硫族化合物半导体是很有前景的谷电子学材料。在该体系所呈现的各种准粒子激发中，谷极化空穴因其在价带中由大的自旋轨道分裂和自旋谷锁定所保留的长谷寿命而格外令人关注。在此我们报道，在没有任何磁场的情况下，单层WSe₂中的此类谷极化空穴能够诱导激子极化子出现惊人的谷分裂。这种分裂的大小与高达7 T的磁场中的塞曼效应相当，并提供了一种定量方法来提取两个谷之间的空穴密度不平衡。我们发现密度差很容易达到每平方厘米超过10¹²，并且它可通过栅极电压以及光激发功率来调节。我们的研究突出了激子极化子对光泵浦的响应，并推进了对单层过渡金属二硫族化合物中谷相关现象的理解。
