Rydberg Exciton Interaction Dynamics

里德伯激子是相当于里德伯原子的固态，并且具有许多令人着迷的特性，例如彼此之间的巨大相互作用直至里德伯封锁点。它们也可以用作检测自由载流子存在的敏感探针，在密度小于0.01电子空穴对/立方微米的情况下，自由载流子会产生类似的阻断效应，称为等离子体阻断。对于旨在利用里德堡阻断的后续实验，能够区分这两种阻断机制并确定地创建它们是至关重要的。与里德伯原子相比，半导体周围导致更快和更复杂的载流子和种群动力学，这需要首先详细了解。例如，预计自由载流子可以快速形成束缚激子状态，而激子可以通过与声子的相互作用而电离，因此在很长一段时间内，通常期望两种封锁机制的混合。因此，本项目的主要目的在于通过时间分辨和空间分辨光谱来更深入地了解复杂的种群动态。为此，该项目旨在通过定制调制器来研究时间解决的Rydberg阻塞，该调制器可以产生持续时间约为500 PS至1 ns的傅里叶限制脉冲。这将使我们能够进行泵探实验，这将揭示等离子体激子形成的速率，里德堡激子的电离速率，它们向低能态的弛豫以及对激子形成等离子体的俄歇辅助。此外，我们将关注传播效应和封锁效率的空间分辨测量，以更深入地了解里德伯激子之间相互作用势的空间依赖性，并了解由不同主量子数的极化子的不同传播速度引起的色散效应是否会导致在晶体内不同位置或不同时间变化的相互作用。最后，我们还将研究偶极禁止激子对其光学活性对应物的影响。这里，我们将重点关注S-激子和d -激子，它们的波函数形状与p -激子的波函数形状有很大不同，这意味着相互作用势可能相当复杂。由于双光子吸收选择规则的改变，我们将使用双光子吸收和二次谐波光谱来有意地激发偶极子禁态。总之，本项目的主要目的在于详细了解cu2o中几种激子和自由载流子态的居群动态及其相互作用。

Rydberg excitons are the solid state equivalent to Rydberg atoms and share many of their fascinating properties, for example huge interactions among each other up to the point of Rydberg blockade. They may also be used as sensitive probes for the presence of freecarriers, which cause similar blockade effects termed Plasma blockade already at densities of less than 0.01 electron-hole-pairs per cubic micrometer. For subsequent experiments aimed at harnessing Rydberg blockade, it is of fundamental importance to be able todistinguish between these two blockade mechanisms and to create them deterministically. In comparison to Rydberg atoms, the semiconductor surrounding causes faster and more complex carrier and population dynamics which need to be understood in detail first.For example, it is expected that free carriers may form bound exciton states quickly, while excitons may be ionized e.g. by interaction with phonons, so for long times, in general a mixture of both Blockade mechanisms is expected. Therefore, the main aim of the presentprojct lies in gaining a deeper understanding of the complex population dynamics via time-resolved and spatially resolved spectroscopy. To this end, this project aims at investigating timeresolved Rydberg blockade with the help of a tailored modulator that creates Fourier-limited pulses with a duration of approximately 500 PS to 1 ns. This will allow us to perform pump-probe experiments, which will shed light on the rate of exciton formation from plasma, theionization rate of Rydberg excitons, their relaxation towards lowerenergy states and the Auger-assisted formation of plasma from paraexcitons. Further, we will focus on propagation effects and spatially resolved measurements of blockade efficiency to gain a deeper understanding of the spatial dependence of the interaction potential between Rydberg excitons and to understand whether dispersion effects resulting from varying propagation velocities ofpolaritons with different principal quantum numbers result in interactions that vary at different positions inside the crystal or at different times. Finally, we will also investigate the influence of dipoleforbidden excitons on their optically active counterparts. Here, we willfocus on S- and D-excitons, which have wavefunctions with a shape that differs significantly from that of P-excitons, which implies that the interaction potential may be rather complicated. Here we will perform two-photon absorption and second-harmonic spectroscopy todeliberately excite the dipole-forbidden states due to the altered selection rules for two-photon absorption. In summary, the main aim of the present project lies in gaining a detailed understanding of the population dynamics of the several exciton and free-carrier states inCu2O and their interactions.