hole doping
n.β Β«In the insulating “parent” materials from which high-temperature superconductors arise, which are typically made of materials containing copper and oxygen, each copper atom has one “free” electron. These electrons, however, are stuck in a Mott insulating stateβthe quantum traffic jamβand cannot move around. By removing a few of the electronsβa process called “hole doping”βthe remaining electrons can start to flow from one copper atom to the next. In essence, this turns the material from an insulator to a metallic state, but one with the startling property that it superconductsβit carries electrical current effortlessly without any losses of energy.Β» ββThe effects of quantum βtraffic jamβ in high-temperature superconductors” Science Centric Aug. 27, 2008. (source: Double-Tongued Dictionary)