Interactions of Rydberg excitons with charged impurities

研究了半导体Cu_2O中里德伯激子与带电杂质的相互作用。在Cu_2O中，可以观察到主量子数高达n=30的里德伯激子和在微米范围内的扩展。与里德伯原子类似，里德伯激子表现出巨大的极化率，这使得可以通过施加小电场来控制它们的状态。在这种情况下，我们预计晶体环境中的里德伯激子产生的里德伯态的性质有显着的影响。静电荷的存在导致电场诱导能级的斯塔克分裂和状态的混合，甚至接近带隙的高能量状态的解离。目前这项提议的目的是调查和控制杂质对里德伯光谱的不利影响。我们将采用双色泵浦探测光谱系统地激发里德伯激子与高主量子数，中和带电杂质的电场。这可能是由于束缚激子复合物的形成或由于激子在杂质处的复合而发生的。为了研究这种中和的微观机制，我们计划测量探测光谱对稳态和时间分辨的低功率泵浦光的光学响应。在低功率下，预期探测态的发射强度会增加。从与探测状态的主量子数的光学响应的缩放，我们将能够确定杂质周围的阻塞体积，其中激子的激发被阻止。与泵浦态的主量子数的缩放使得有可能确定相互作用背后的确切机制。使用时间分辨激发和检测，我们将能够测量中和的时间尺度以及杂质的再电离。里德伯激子和带电杂质之间的相互作用的深入理解是根本相关的观察里德伯激子具有较高的主量子数和傅立叶有限线宽的Cu2O，但也其他材料系统，如TMDC。

We investigate the interaction between Rydbergexcitons and charged impurities in the semiconductor Cu2O. In Cu2O, Rydbergexcitons with principal quantum numbers up to n=30 and extensions in the micrometer range can be observed. In analogy to Rydbergatoms, Rydbergexcitons exhibit an enormous polarizability, which renders it possible to control their state by the application of small electric fields. In this context, we expect the crystalline environment in which Rydbergexcitons are created to have a significant impact on the properties of the Rydbergstates. The presence of static electric charges leads to an electric field inducing a Stark-splitting of energy levels and mixing of states or even dissociation of energetically high states close to the band gap. The aim of the proposal at hand is to investigate and to control this detrimental impact of the impurities on the Rydberg spectrum. We will employ two-color pump-probe spectroscopy to systematically excite Rydbergexcitons with high principal quantum numbers that neutralize the electric fields of charged impurities. This may happen due to the formation of a bound exciton complex or due to the recombination of an exciton at the impurity. To investigate the microscopic mechanism of this neutralization, we plan to measure the optical response of the probed spectrum to a low-power pump beam in the steady-state as well as time-resolved. At low powers, an increase of oscillatorstrength of the probed state is expected. From the scaling of the optical response with the principal quantum number of the probed state we will be able to determine the blockade volume around an impurity, within which the excitation of excitons is blocked. The scaling with the principal quantum number of the pumped state renders it possible to determine the exact mechanism behind the interaction. Using time-resolved excitation and detection we will be able to measure the time scales of the neutralization as well as the reionization of the impurities. A deepened understanding of the interaction between Rydbergexcitons and charged impurities is of fundamental relevance to observe Rydbergexcitons with higher principal quantum numbers and Fourier-limited linewidths in Cu2O, but also other material systems, such as TMDCs.