Iron is not a superconductor at ambient conditions, but becomes superconducting at very low temperatures. The same phenomenon is observed other iron-based materials (e.g. iron selenide). Superconductivity is enabled by the so-called Cooper pairs - pairs of electrons that interact with each other and condense to a single quantum state. The transition temperature to superconducting state (Tc) is enhanced by lowering temperature, and the higher Tc can be reached by material engineering, e.g. by adding other atoms to iron. Deep freezing simply removes thermal disruptions and improves the overall quality of the superconducting material.