Quantum Trick Makes Metals Become Insulators

The investigation of complex materials such as high-temperature superconductors is problematic because of the presence of disorder and many competing interactions in real crystalline materials. "This makes it difficult to identify the role of specific interactions and, in particular, to decide whether repulsive interactions between electrons alone can explain high-temperature superconductivity," says Dr. Theodoulos Costi from the Institute of Solid State Research, Forschungszentrum Jülich, which is a member of the Helmholtz Association. ... The physicists succeeded in simulating one of the most dramatic electronic phenomena with the aid of this quantum simulator: when the interactions between the electrons become too strong, a metal can suddenly become insulating. The resulting so-called Mott insulator is probably the most important example of a state of strong electronic interactions in condensed matter physics, as it is a starting point for the investigation of quantum magnetism. In addition, high-temperature superconductivity is found to arise in close proximity to this insulator. ... - sd