Theme 3 colloquium: '2D quantum materials on demand: twisting, stacking & defect engineering' (Lecture)

Quantum materials are of increasing interest and relevance for technological applications as well as in fundamental sciences. Quantum materials host controllable quantum states and emerging phases driven by various interactions. 2D quantum materials can be precisely tailored on the atomistic level and integrated in opto-electronic circuits towards applications in the fields of quantum computation, sensing, information and cryptography. Interactions in 2D quantum systems can be engineered by stacking, precise twisting or by selectively inducing defects. In-situ control can be realized by external stimuli such as electric or magnetic field and charge doping in field effect structures. We demonstrate strong exciton dominated light-matter interaction in semiconducting transition metal dichalcogenides (SC-TMDCs) monolayers, van der Waals hybrid-structures and defect engineered quantum emitter structures. We will discuss recent developments in the area of electric field controlled multi-valley physics and condensation signatures in TMDC hetero-bilayers. Furthermore, we will introduce a rather new class of 2D materials, 2D polar metals and focus on their linear optical response measured by spectroscopic ellipsometry.

We acknowledge funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany´s Excellence Strategy – EXC 2089/1 – 390776260 and projects Wu 637/4- 1, 4 – 2, 7-1 and SPP 2244.