Surprising electronic disorder in a copper oxide-based ceramic
Cuprates, a class of copper-oxide ceramics that share a common building block of copper and oxygen atoms in a flat square lattice, have been studied for their ability to be superconducting at extremely high temperatures. In their pristine state, however, they are a special kind of insulator (a material that does not readily conduct electricity) known as a Mott insulator. When electrical charge carriers — either electrons or the lack of electrons, known as "holes" — are added to an insulator in a process called doping, the insulator may become a metal, which readily conducts electricity, or a semiconductor, which can conduct electricity depending on the environment. Cuprates, however, behave neither like a normal insulator nor like a normal metal because of strong interactions between their electrons. To avoid the large energy cost arising from these interactions, the electrons spontaneously organize in a collective state where the motion of each particle...