J. Robert Schrieffer (1931–2019)

With the passing away of Robert Schrieffer a few days ago, one of the pioneering figures in modern theoretical physics is no more. Schrieffer, as a Ph D student, working with his mentor John Bardeen and postdoctoral colleague Leon Cooper, gave to the world the microscopic theory of superconductivity in 1957. (Their theory, unbreakably supported by a host of experiments, is considered the gold standard for the atomic-level understanding of the behaviour of electrons in matter, indeed of all fermions.) The flow of electrical current without any resistance, suddenly turning on in a very cold metal (close to, but above the absolute zero of temperature) is one of the most spectacular and mysterious phenomena in physical sciences. Discovered in 1911, its seductive appeal lured almost all the great names of physics into (unsuccessful) efforts at making sense of the phenomenon.