Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA , 143 avenue de Rangueil, 31400 Toulouse, France.
Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology , Wybrzeze Wyspianskiego 27, 50-370 Wrocaw, Poland.
Nano Lett. 2017 Oct 11;17(10):6360-6365. doi: 10.1021/acs.nanolett.7b03184. Epub 2017 Sep 18.
Stacking atomic monolayers of semiconducting transition metal dichalcogenides (TMDs) has emerged as an effective way to engineer their properties. In principle, the staggered band alignment of TMD heterostructures should result in the formation of interlayer excitons with long lifetimes and robust valley polarization. However, these features have been observed simultaneously only in MoSe/WSe heterostructures. Here we report on the observation of long-lived interlayer exciton emission in a MoS/MoSe/MoS trilayer van der Waals heterostructure. The interlayer nature of the observed transition is confirmed by photoluminescence spectroscopy, as well as by analyzing the temporal, excitation power, and temperature dependence of the interlayer emission peak. The observed complex photoluminescence dynamics suggests the presence of quasi-degenerate momentum-direct and momentum-indirect bandgaps. We show that circularly polarized optical pumping results in long-lived valley polarization of interlayer exciton. Intriguingly, the interlayer exciton photoluminescence has helicity opposite to the excitation. Our results show that through a careful choice of the TMDs forming the van der Waals heterostructure it is possible to control the circular polarization of the interlayer exciton emission.
堆叠具有半导体性质的过渡金属二卤化物（TMD）的原子单层已成为工程化其性质的有效方法。原则上，TMD 异质结构的能带交错排列应该导致具有长寿命和稳健谷极化的层间激子的形成。然而，这些特征仅在 MoSe/WSe 异质结构中同时观察到。在这里，我们报告了在 MoS/MoSe/MoS 三层范德华异质结构中观察到长寿命层间激子发射的情况。通过光致发光光谱以及通过分析层间发射峰的时间、激发功率和温度依赖性，证实了观察到的跃迁的层间性质。观察到的复杂光致发光动力学表明存在准简并动量直接和动量间接能隙。我们表明，圆偏振光泵浦导致层间激子的长寿命谷极化。有趣的是，层间激子光致发光的螺旋性与激发相反。我们的结果表明，通过仔细选择形成范德华异质结构的 TMD，可以控制层间激子发射的圆偏振。
