Electrons that stick together, superconduct together

The discovery of a surprising feature of superconductivity in an unconventional superconductor by a RIKEN-led research team provides clues about the superconducting mechanism in this material and thus could aid the search for room-temperature superconductors ("Emergent loop-nodal s+--wave superconductivity in CeCu2Si2: Similarities to the iron-based superconductors").

Superconductors conduct electricity with zero resistance, and hence they could potentially revolutionize electric motors, generators and utility grids. However, scientists have yet to discover a material that becomes superconducting at ambient temperature—all known superconductors operate only at cryogenic temperatures, making them impractical for general applications. Unfortunately, progress toward achieving the goal of room-temperature superconductivity has been hindered by scientists’ limited understanding of the fundamental mechanism responsible for the emergence of this remarkable physical phenomenon.

Superconductivity occurs as the result of pairs of electrons binding together in such a way that they act as a single quasiparticle. In conventional superconductors, which include elemental materials that become superconducting at temperatures very close to absolute zero, the binding force is provided by vibrations in the atomic lattice through which the electrons travel.

Yet not all superconductors behave this way. In unconventional superconductors that do not fit the conventional model, this binding force develops in a different manner and various mechanisms have been proposed for it. One such mechanism is the magnetic or spin fluctuation of the electrons themselves, which binds electrons in pairs through the entanglement of electron spins. However, recent experiments have shown that this mechanism cannot explain the superconducting state in the quintessential unconventional superconductor CeCu2Si2.