Propagation dynamics of exciton-electron complexes in atomically-thin semiconductors

原子薄层的过渡金属二卤化物是研究相互作用电子多粒子态的一个很好的平台。从基础物理和应用的角度来看，一个特别有趣的场景是，束缚电子-空穴复合体(称为激子)和自由电荷载流子同时存在。由于它们对光学响应的强烈影响，这些复合玻色-费米混合物的性质是这些体系中一个非常热门的研究课题。然而，尽管人们在静态极限下很好地理解了所产生的三子和费米极化子复合体的物理，但对于这些态的传播动力学，关于线性和非线性现象，人们知之甚少。此外，最近证明在单层半导体中在实验可达的条件下出现电子的维格纳相，开启了对一种非常不寻常和有趣的场景的研究，涉及激子在电子晶体中的运动。这促使这一提议的主要目的是发展对多粒子过程的微观理解，该过程决定了激子-电子复合体在原子薄半导体中的传播动力学。重点在于了解与激子-载流子混合物相关的非线性现象，以及相关电子Wigner态对激子输运的影响。我们将结合先进的微观多粒子方法和栅极可调样品的瞬变显微镜来监测激子复合体在时间、能量和空间中存在自由电荷时的行为。最终，这将使我们能够解决电子关联对激子复合体物理的影响，超越邻近屏蔽效应，扩展到激子动力学和输运的领域。我们希望为可移动激子-电子准粒子的非线性现象提供一个全面的图景，并提供通往外部可调谐和控制的路径。

Atomically-thin layers of semiconducting transition metal dichalcogenides emerged as an excellent platform to study interacting electronic many-particle states. A particularly interesting scenario, relevant from both fundamental physics and applications perspectives, it the simultaneous presence of bound electron-hole complexes, known as excitons, and free charge carriers. The properties of these composite Bose-Fermi mixtures are a topic of intense research in these systems due to their strong impact on the optical response. However, while the physics of the resulting trion and Fermi polaron complexes are well understood in the static limit, little is known about the propagation dynamics of these states, with respect to both linear and non-linear phenomena. Moreover, recently demonstrated emergence of Wigner phases of electrons in monolayer semiconductors at experimentally accessible conditions opens up studies of a very unusual and intriguing scenario involving excitons moving through an electron crystal. This motivates the main aim of this proposal to develop a microscopic understanding of the many-particle processes determining propagation dynamics of exciton-electron complexes in atomically-thin semiconductors. The focus lies on understanding non-linear phenomena associated with the exciton-carrier mixtures as well as the impact of correlated electronic Wigner states on the exciton transport. We will combine advanced microscopic many-particle methods with transient microscopy of gate-tunable samples to monitor the behavior of excitonic complexes in the presence of free charges in time, energy, and space. Ultimately, this should allow us to address the influence of electronic correlations on the physics of exciton complexes, reaching beyond proximity screening effects into the realm of exciton dynamics and transport. We envision to offer a comprehensive picture for non-linear phenomena of mobile exciton-electron quasiparticles with pathways towards external tunability and control.