Wang Tianmeng, Miao Shengnan, Li Zhipeng, Meng Yuze, Lu Zhengguang, Lian Zhen, Blei Mark, Taniguchi Takashi, Watanabe Kenji, Tongay Sefaattin, Smirnov Dmitry, Shi Su-Fei
Department of Chemical and Biological Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States.
National High Magnetic Field Lab , Tallahassee , Florida 32310 , United States.
Nano Lett. 2020 Jan 8;20(1):694-700. doi: 10.1021/acs.nanolett.9b04528. Epub 2019 Dec 26.
Transition metal dichalcogenides (TMDCs) heterostructure with a type II alignment hosts unique interlayer excitons with the possibility of spin-triplet and spin-singlet states. However, the associated spectroscopy signatures remain elusive, strongly hindering the understanding of the Moiré potential modulation of the interlayer exciton. In this work, we unambiguously identify the spin-singlet and spin-triplet interlayer excitons in the WSe/MoSe heterobilayer with a 60° twist angle through the gate- and magnetic field-dependent photoluminescence spectroscopy. Both the singlet and triplet interlayer excitons show giant valley-Zeeman splitting between the K and K' valleys, a result of the large Landé g-factor of the singlet interlayer exciton and triplet interlayer exciton, which are experimentally determined to be ∼10.7 and ∼15.2, respectively, which is in good agreement with theoretical expectation. The photoluminescence (PL) from the singlet and triplet interlayer excitons show opposite helicities, determined by the atomic registry. Helicity-resolved photoluminescence excitation (PLE) spectroscopy study shows that both singlet and triplet interlayer excitons are highly valley-polarized at the resonant excitation with the valley polarization of the singlet interlayer exciton approaching unity at ∼20 K. The highly valley-polarized singlet and triplet interlayer excitons with giant valley-Zeeman splitting inspire future applications in spintronics and valleytronics.
具有II型排列的过渡金属二硫属化物（TMDCs）异质结构拥有独特的层间激子，其可能处于自旋三重态和自旋单重态。然而，相关的光谱特征仍然难以捉摸，这严重阻碍了对层间激子的莫尔势调制的理解。在这项工作中，我们通过依赖于栅极和磁场的光致发光光谱，明确地识别了具有60°扭转角的WSe/MoSe异质双层中的自旋单重态和自旋三重态层间激子。单重态和三重态层间激子在K和K'谷之间均表现出巨大的谷-塞曼分裂，这是由于单重态层间激子和三重态层间激子的大朗德g因子导致的，实验确定其分别约为10.7和15.2，这与理论预期高度吻合。来自单重态和三重态层间激子的光致发光（PL）表现出相反的螺旋性，这由原子配准决定。螺旋度分辨光致发光激发（PLE）光谱研究表明，在共振激发下，单重态和三重态层间激子均具有高度的谷极化，单重态层间激子在约20 K时谷极化接近1。具有巨大谷-塞曼分裂的高度谷极化单重态和三重态层间激子为自旋电子学和谷电子学的未来应用带来了启发。
