Superconductivity Induced in Iron Telluride Films by Low Temperature Oxygen Incorporation

We report superconductivity induced in films of the non-superconducting, antiferromagnetic parent material FeTe by low temperature oxygen incorporation in a reversible manner. X-ray absorption shows that oxygen doping changes the nominal Fe valence state from 2+ in the non-superconducting 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$_{1-x}$Se$_x$. This work also suggests a convenient path for conducting doping experiments in-situ with many measurement techniques.