Bulk superconductivity in FeTe1−xSex via physicochemical pumping of excess iron

The iron-based superconductor FeTe1-xSex has attracted considerable attention as a candidate
topological superconductor owing to a unique combination of topological surface states and bulk
high-temperature superconductivity. The superconducting properties of as-grown single crystals,
however, are highly variable and synthesis dependent due to excess interstitial iron impurities incor-
porated during growth. Here we report a novel physicochemical process for pumping this interstitial
iron out of the FeTe1-xSex matrix and achieving bulk superconductivity. Our method should have
signicant value for the synthesis of high-quality single crystals of FeTe1-xSex with large supercon-
ducting volume fractions.