  Understanding the fundamental mechanisms ruling laser-induced coherent charge
transfer in hybrid organic/inorganic interfaces is of paramount importance to
exploit these systems in next-generation opto-electronic applications. In a
first-principles work based on real-time time-dependent density-functional
theory, we investigate the ultrafast charge-carrier dynamics of a prototypical
two-dimensional vertical nanojunction formed by a MoSe$_2$ monolayer with
adsorbed pyrene molecules. The response of the system to the incident pulse,
set in resonance with the frequency of the lowest-energy transition in the
physisorbed moieties, is clearly nonlinear. Under weak pulses, charge transfer
occurs from the molecules to the monolayer while for intensities higher than
1000 GW/cm$^{2}$, the direction of charge transfer is reverted, with electrons
being transferred from MoSe$_2$ to pyrene. This finding is explained by Pauli
blocking: laser-induced (de)population of (valence) conduction states saturates
for intensities beyond 200 GW/cm$^{2}$. Evidence of multi-photon absorption is
also provided by our results. A thorough analysis of electronic current
density, excitation energy, and number of excited electrons supports the
proposed rationale and suggests the possibility to create an inorganic/organic
coherent optical nanojunction for ultrafast electronics.
