The ability of certain materials to conduct electric current with virtually no resistance is known as superconductivity. This ability has interesting and potentially useful consequences. Low temperatures are required for a material to behave as a superconductor.
Aluminum, niobium, magnesium diboride, cuprates such as yttrium barium copper oxide, and iron pnictides are all examples of superconductors. Only at temperatures below a certain threshold, known as the critical temperature, these materials become superconductors.