Taming Charged Defects: Large Scale Purification in Semiconductors using Rydberg Excitons

We investigate the interaction between highly excited Rydberg excitons and charged impurities in the semiconductor Cuprous Oxide. We find that it is long-ranged and based on charge-induced dipole interactions. We demonstrate that we can utilize this interaction to neutralize impurities throughout the whole crystal - an effect we call purification. Purification reduces detrimental electrical stray fields drastically. We find that the absorption of the purified crystal increases by up to 25 % and that the purification effect is long-lived and may persist for hundreds of microseconds or even longer. Using a time-resolved pump-probe technique, we can discriminate purification from Rydberg blockade, which has been a long-standing goal in excitonic Rydberg systems.