Excitonic Physics of Transition Metal Dichalcogenide Monolayers and Heterostructures

由于电子与空穴之间的约束增强型库仑相互作用，过渡金属二卤化物单分子膜的光学物理和应用主要由激子态和三电子态主导。这些态的强束缚性质意味着大波矢暗激子态即使在室温下也是稳定的。虽然这些态对发光和激子线宽的间接影响是众所周知的，但目前对它们的唯一直接探测是双共振拉曼散射。在这些材料的同质和异质双层中观察到的莫尔效应是另一个热门话题。在这里，拉曼散射可以用来直接探测莫尔矢量，并通过将激发源调节到不同的电子共振，可以探测不同的激子态如何与莫尔结构相互作用。在异质双层中，将特定的拉曼峰与每一层特有的声子相关联的能力意味着可以使用拉曼散射来探测两层之间激子的杂化。我的项目将包括使用共振拉曼散射和其他高分辨率激光光谱仪来研究这些极其重要的材料中的激子，特别是暗激子物理。在这个项目中，我将研究同位素纯的二元材料、四元合金以及应变对通过共振拉曼散射获得的亮激子和暗激子状态的影响。

The optical physics and applications of the transition metal dichalcogenide monolayer are dominated by excitonic and trionic states due to the confinement-enhanced coulomb interactions between electrons and holes. The strongly bound nature of these states means that large wavevector dark excitonic states are stable even at room temperature. Whilst the indirect effect of these states on luminescence and excitonic linewidths is well established the only direct probe of them currently is double resonance Raman scattering. Moire effects observed in homo and heterobilayers of these materials are another hot topic. Here Raman scattering can be used to directly probe the moire vectors and by tuning the excitation source to different electronic resonances it is possible to probe how the different excitonic states interact with the moire structure. In heterobilayers the ability to associate particular Raman peaks with phonons unique to each layer means that Raman scattering can be used to probe the hybridisation of excitons between the two layers. My project will involve the use of resonance Raman scattering and other high resolution laser spectroscopies to study the excitonic, particularly dark excitonic, physics in these extremely important materials. During the project I will study isotopically pure binary materials, quaternary alloys and the effect of strain on the bright and dark excitonic states accessible via resonance Raman scattering.