nonsuperconducting

Nonsuperconducting is a term used to describe a material that does not exhibit superconductivity under specified conditions. Superconductivity is a quantum phenomenon in which a material's electrical resistance vanishes and magnetic fields are expelled (Meissner effect) below a characteristic critical temperature, and within critical magnetic fields or current densities. A material's classification as nonsuperconducting is conditional: it may be nonsuperconducting at room temperature, at ambient pressure, or for a particular chemical composition, while under other conditions it may become superconducting.

Determination typically involves electrical resistivity measurements as a function of temperature, magnetic susceptibility tests, and sometimes specific-heat measurements. If the resistivity remains finite down to the lowest temperatures accessible, and no Meissner response is observed, the material is considered nonsuperconducting under those conditions. Nonsuperconductivity can arise from several factors: lack of the Cooper pairing mechanism, strong electron scattering, magnetic ordering, or structural distortions that prevent the formation of the superconducting state. The boundary between superconducting and nonsuperconducting behavior is defined by Tc, Hc, and Jc for a given material.

Many common materials are nonsuperconducting under standard laboratory conditions; superconductivity is observed only in a subset of materials and often only under specific atmospheres or extreme conditions such as high pressure or chemical doping. In recent decades, researchers have discovered superconductivity in various hydrides and other compounds at high pressures and, more recently, at higher temperatures, illustrating that nonsuperconducting can be a state that becomes superconducting under sufficient tuning. Related topics include superconductivity, the Meissner effect, and critical temperature.