Discovery of two-phase superconductivity in CeRh2As2

The phenomenon of superconductivity, providing current transmission without dissipation and a host of unique magnetic properties arising from macroscopic quantum coherence, was first discovered over a century ago. It was not understood until 1957, after which it quickly became clear that superconductors could in principle exist with a wide variety of the fundamental characteristic often referred to as the order parameter. Until the late 1970’s, however, all superconductors found experimentally had the same class of order parameter. Since then many aspects of the expected variety of order parameters have been discovered, but one surprising fact remained.