Charge carrier scattering and ultrafast Auger dynamics in two-dimensional superatomic semiconductors

Superatom solids are promising for optoelectronic applications, owing to their tunable structural and electronic properties; yet, the electronic transport properties of these materials have been largely unexplored. Here, we report the Auger recombination dynamics of free carriers in two representative two-dimensional superatomic semiconductors, Re6Se8Cl2 and Mo6S3Br6, studied using ultrafast terahertz photoconductivity measurements. The fast Auger recombination dynamics are characterized by a cubic dependence of the Auger rate on carrier density in Re6Se8Cl2 and a quadratic dependence in Mo6S3Br6. The effective lifetimes of Mo6S3Br6 (similar to 0.5 ps) are over an order of magnitude shorter than those (similar to 20 ps) of Re6Se8Cl2. These results highlight the variability of the optoelectronic properties of different superatom solids.