Thorsten Deilmann: Dark and bright electronic excitations in layered materials

Thorsten Deilmann and Kristian Sommer Thygesen Center for Atomic-Scale Materials Design (CAMD), Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark Among low-dimensional materials layered structures like hexagonal boron nitride, or transition metal dichalcogenide monolayers like MoS2 are promising candidates for next-generation opto- electronic with optical properties which are dominated by excitons. In the presence of additional charges due to doping by a substrate or vacancies, trions (i.e. charged excitons) can occur in the optical spectrum. This opens a route towards a specific manipulation of the properties by light and by charging, e.g., due to an externally applied gate voltage. Recently, we have developed a first-principle many-body approach [1] based on the framework of many-body perturbation theory for excited electronic states which is able to describe excitons and trions on equal footing. Here, we apply this method to different layered materials and discuss their spectra, energy compositions, and correlated wave functions. E.g., for WSe2 we find optically active trions red-shifted compared to the excitons, confirming experimental findings. [1] T. Deilmann, M. Drüppel, and M. Rohlfing, Phys. Rev. Lett. 116 (2016), 196084. Thorsten Deilmann is currently working as Postdoc at the Technical University of Denmark. His main focus are excited states (excitons and trions) in low-dimensional materials. He received his B.Sc. (2010) and M.Sc. (2012) at the University of Münster, where he also finished his PhD in 2016.