论文标题
激子转换为室温单层中的山谷两极分化的控制机制WS $ _ \ text {2} $
Exciton-to-trion conversion as a control mechanism for valley polarization in room-temperature monolayer WS$_\text{2}$
论文作者
论文摘要
过渡金属二北元（TMD）单层是二维半导体，其带状结构中有两个山谷，可以使用圆形偏振光选择性地解决。它们的光致发光光谱的特征是中性和带电的激子（TRIONS），形成了由净电荷密度控制的化学平衡。在这里，我们使用化学掺杂将激子转化为$ \ text {ws} _ {2} $单层在室温下的转化，并通过在山谷选择性光学激发下通过光致发光测量来研究所得的山谷极化。我们表明，掺杂导致发射由与快速非辐射重组相关的强山谷极化的Trions主导。同时，由于转化为TRIONS，掺杂导致强烈淬灭但高度偏振的激子发射。速率方程模型用掺杂控制的激子 - 轨道平衡来解释观察到的山谷极化。我们的结果阐明了激子 - 轨道转换在单层TMD中山谷极化的重要作用。
Transition metal dichalcogenide (TMD) monolayers are two-dimensional semiconductors with two valleys in their band structure that can be selectively addressed using circularly polarized light. Their photoluminescence spectrum is characterized by neutral and charged excitons (trions) that form a chemical equilibrium governed by the net charge density. Here, we use chemical doping to drive the conversion of excitons into trions in $\text{WS}_{2}$ monolayers at room temperature, and study the resulting valley polarization via photoluminescence measurements under valley-selective optical excitation. We show that the doping causes the emission to become dominated by trions with a strong valley polarization associated with rapid non-radiative recombination. Simultaneously, the doping results in strongly quenched but highly valley-polarized exciton emission due to the enhanced conversion into trions. A rate equation model explains the observed valley polarization in terms of the doping-controlled exciton-trion equilibrium. Our results shed light on the important role of exciton-trion conversion on valley polarization in monolayer TMDs.
