Light-matter coupling with two-dimensional tellurides

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The project focuses on fundamental investigations of the optical properties of elementary manybody excitations in atomically thin transition-metal dichalcogenide layers, composed of MoTe2 and MoWTe2 in their semiconducting 2H phase. We will study advanced light-matter coupling, with a particular emphasize on the formation, valley-selective dynamic scattering and condensation of exciton-polaritons, emerging in these monolayers, by embedding them monolayers in custom-designed dielectric microcavities. The first objective is to investigate the optical properties of many body-states and fundamental excitations in 2H-MoTe2 and 2H-MoWTe2 monolayers via different spectroscopy techniques. By optimizing sample preparation techniques, substrates, and capping procedures, we will systematically improve the optical quality of the materials. We will furthermore explore, to what extent the optical transitions in the ternary 2H-MoWTe2 layers, as well as strain- and dielectrically engineered 2H-MoTe2 can reach the important telecom window at 1.3 µm. The second objective is to implement a room-temperature polaritonic device-platform operating in the near- infrared spectral range utilizing atomically thin MoTe2 and MoWTe2.While dielectric microcavities with low mode volumes and high-quality factors >103 for the integration of MoSe2 and WSe2 recently became available, we will push forward this technology to enter the important spectral range around 1.3 µm. Once the strong coupling regime between Mo(W)Te2 monolayers and the optical cavity resonance is established, dynamic relaxation and scattering effects of polaritons, intrinsic non-linearities and the final state bosonic stimulation leading to dynamical polariton condensation , will be explored in detail. MoTe2 based polaritonic nonlinear devices, in particular operated in the Telecommunication window are elusive. Apart from gaining a deeper understanding in the physics and optical properties of 2H-MoTe2 and 2H-MoWTe2 monolayers, a successful implementation of polariton condensates at 1300 nm, as foreseen in this project, would compose a major breakthrough towards the implementation of ultra-low threshold nanolasers based on ultimately thin gain materials.