hole doping
n.— «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 state—the quantum traffic jam—and cannot move around. By removing a few of the electrons—a process called “hole doping”—the 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 superconducts—it carries electrical current effortlessly without any losses of energy.» —“The effects of quantum ‘traffic jam’ in high-temperature superconductors” Science Centric Aug. 27, 2008. (source: Double-Tongued Dictionary)