Optical-field induced transient optics and exciton dynamics in transition metal dichalcogenide hetero-bilayers*

Two-dimensional (2D) heterostructures offer a new platform for exploring low-dimensional physics. Due to the strong light–matter interactions and direct-bandgap properties, mono- and few-layer transition-metal dichalcogenides (TMDs) further attract a lot of interest for possible optoelectronic applications. In particular, the type II band-alignment TMDs heterostructures provide interesting opportunities to investigate real-time dynamics of different excitons.  Although recent advanced pump–probe spectroscopies have provided rich experimental data, their accurate theoretical description and understanding remain under explored. In this work, we investigate from first-principles optical-field induced transient optics and exciton dynamics in type II TMD bilayers, employing the time-dependent adiabatic GW method (TD-aGW) with real-time propagation of the density matrix [1]. Strong excitonic effect (electron-hole interaction) is discovered to play a vital role on the dynamic processes. Our results reveal a new picture of fast dynamic coupling between inter- and intra-layer excitons, contrary to previously believed single-particle charge transfer scenario. We compute the transient optical properties from TD-aGW corresponding to the pump-probe setup (which are directly observable quantities in most experiments).