Special Condensed Matter Seminar: Strongly correlated electrons and Feshbach resonances in two-dimensional semiconductor bilayers

In this talk, I will present recent experiments where we investigated the many-body physics of electrons and excitons in two-dimensional transition metal dichalcogenides (TMDs). For our investigation, we used a structure composed of encapsulated MoSe2 homobilayer separated by a monolayer hBN tunnel barrier, where top and bottom gates enable independent control of the chemical potential and the electric field. I will describe a method that utilizes the energy shift of the exciton-polaron resonance to detect a layer-resolved charge configuration. Using this method, we found a periodic chemical potential dependence on carrier filling, indicating the existence of moiré subbands. Electric field tuning at a filling of one electron per moiré unit cell results in abrupt interlayer charge transfer, evidencing the emergence of a strongly correlated incompressible electronic state. In this state, a new exciton umklapp resonance appears, evidencing the emergence of a periodic charge distribution. Furthermore, by hole doping, we realized a tunnel coupled moiré lattice, where we observed an electric field and moiré site-dependent inter-layer coherent tunneling. Finally, I will show an electrically tunable two-dimensional Feshbach resonance in exciton-hole scattering, which allows us to control the strength of interactions between excitons and holes located in different layers.