Optical excitations in transition metal dichalcogenide heterostructures under pressure

该项目的主要目标是获得过渡金属二硫属化物异质结构的层间耦合的全面理解。在许多情况下，层间的相互作用导致出现的电子和光学性质是从根本上不同于那些组成层。关键参数是层间耦合强度及其莫尔图案。它由材料和制造工艺的选择给出，并且通常被认为是系统的不可改变的属性。然而，施加的流体静压或单轴压力强烈影响层间距离，从而影响电子耦合。因此，可以通过压力来调谐层间激子和莫尔带。在我们的联合实验理论的努力，我们将制造过渡金属二硫属化物的异质结构，并研究其（瞬态）光学性能取决于压力。实验技术包括（超快）光致发光，吸收和二次谐波产生光谱。作为一种理论方法，我们将使用从头算多体研究和模型开发的组合来解决所研究系统的大小。此外，我们将设计压缩应变景观，这将允许层间激子的函数，并最终调查集体现象，如玻色-爱因斯坦凝聚。

The main goal of the project is to gain a comprehensive understanding of interlayer coupling in transition metal dichalcogenide heterostructures. In many cases, interlayer interactions lead to emergent electronic and optical properties that are fundamentally distinct from those of the constituent layers. A critical parameter is the interlayer coupling strength with its moiré pattern. It is given by the choice of the materials and the fabrication process, and is typically considered as an unchangeable property of the system. Applied hydrostatic or uniaxial pressure, however, strongly affects the interlayer distance and thus the electronic coupling. Therefore, one can tune the interlayer excitons and moiré bands by pressure. In our joint experiment-theory effort, we will fabricate heterostructures of transition metal dichalcogenides and investigate their (transient) optical properties depending on pressure. Experimental techniques comprise (ultrafast) photoluminescence, absorption and second harmonic generation spectroscopy. As a theoretical approach, we will use a combination of ab-initio many-body investigations and model development to tackle the size of the investigated system. Furthermore, we will engineer compressive strain landscapes, which will allow for funneling of interlayer excitons and eventually the investigation of collective phenomena such as Bose-Einstein condensation.