Probing excitons in transition metal dichalcogenides by Drude-like exciton intraband absorption
Probing excitons in transition metal dichalcogenides by Drude-like exciton intraband absorption
复制标题
通过类德鲁德激子带内吸收探测过渡金属二硫属化物中的激子
作者：
Zhao Siqi;He Dawei;He Jiaqi;Zhang Xinwu;Yi Lixin;Wang Yongsheng;Zhao Hui
了解二维半导体过渡金属二硫族化合物的激子动力学对于发展其光电应用具有重要意义。最近，基于共振激子吸收的瞬态吸收技术已被用于研究这些材料中激子动力学的各个方面。这种测量中的瞬态吸收源于相空间状态填充、带隙重整化或屏蔽效应。在这里，我们报告了一种新的方法来探测激子动力学的基础上激子带内吸收。在这种类似德鲁德的过程中，探测光子在其带内激发中被激子吸收到更高的能量状态，从而引起瞬态吸收信号。虽然瞬态吸收的幅度低于共振技术，但新方法对探测波长的选择限制较少，具有更大的线性范围，并且可以提供关于光载流子动力学的补充信息。以WS 2单层和体样品为例，我们表明，新方法可以探测激子-激子湮灭在高密度和揭示激子形成过程。我们还发现WS 2单层的激子带内吸收截面约为10 - 18 cm 2。
Understanding excitonic dynamics in two-dimensional semiconducting transition metal dichalcogenides is important for developing their optoelectronic applications. Recently, transient absorption techniques based on resonant excitonic absorption have been used to study various aspects of excitonic dynamics in these materials. The transient absorption in such measurements originates from phase-space state filling, bandgap renormalization, or screening effects. Here we report a new method to probe excitonic dynamics based on exciton intraband absorption. In this Drude-like process, probe photons are absorbed by excitons in their intraband excitation to higher energy states, causing a transient absorption signal. Although the magnitude of the transient absorption is lower than that of the resonant techniques, the new method is less restrictive on the selection of probe wavelength, has a larger linear range, and can provide complementary information on photocarrier dynamics. Using the WS2 monolayer and bulk samples as examples, we show that the new method can probe exciton–exciton annihilation at high densities and reveal exciton formation processes. We also found that the exciton intraband absorption cross section of the WS2 monolayer is on the order of 10−18 cm2.