Superconductivity induced in iron telluride films by low-temperature oxygen incorporation

We report superconductivity induced in films of the nonsuperconducting, antiferromagnetic parent material FeTe by low-temperature oxygen incorporation in a reversible manner. X-ray absorption shows that oxygen incorporation changes the nominal Fe valence state from $2+$ in the nonsuperconducting state to mainly $3+$ in the superconducting state. Thus superconductivity in O-doped FeTe occurs in a quite different charge and strain state than the more common FeTe_1-xSeₓ. This work also suggests a convenient path for conducting doping experiments in situ with many measurement techniques.