Electrical resistivity and conductivity ions. In biological membranes, currents are carried by ionic salts. Small holes in cell membranes, called ion channels, are selective to specific ions and determine the membrane resistance. The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In ordinary conductors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a real sample of a normal conductor shows some resistance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing in a loop of superconducting wire
Metallic hydrogen metallized and become superconducting by M.I. Eremets "et al.". This claim is disputed, and their results have not been repeated. In 2011 Eremets and Troyan reported observing the liquid metallic state of hydrogen and deuterium at static pressures of . This claim was questioned by other researchers in 2012. In 2015, scientists at the Z Pulsed Power Facility announced the creation of metallic deuterium using dense liquid deuterium, an electrical insulator-to-conductor transition associated with an increase in optical reflectivity. On 5 October 2016, Ranga Dias and Isaac F. Silvera of Harvard University released claims of experimental evidence that solid metallic