The year 1911 was remarkable for physics in several respects. Ernest Rutherford postulated the existence of the atomic nucleus, which led him to his atom model; Max Planck introduced the quantum concept of zero-point motion; and Heike Kamerlingh Onnes announced the discovery of superconductivity in mercury below a critical transition temperature (see the article by Dirk van Delft and Peter Kes in PHYSICS TODAY, September 2010, page 38). All three discoveries are equally revolutionary, and all helped pave the way for the transition from a classical to a quantum mechanical picture of our world.

The superconducting phase is only one of the possible phases a metal can enter when cooled down. Nature preferred to acquaint humans first with another possible metallic phase, the ferromagnetic one. Both phases are fundamental and are direct, macroscopic manifestations of microscopic many-body quantum physics. But the two phases are largely incompatible.

The past decade,...

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