High T_c Materials

Abstract

High-temperature superconductivity was first discovered by Georg Bednorz and Alex Müller in an unlikely mixture of La-Ba-Cu-O [1]. This was back in 1986, when Neutron News was no more than a gleam in Gerry Lander's eye. The superconducting transition temperature, T_c, of this new material was ∼30 K, which was substantially above the previous record of 23 K. The discovery, which was quite surprising given that transition-metal oxides were generally considered to be poor conductors, initiated a huge wave of excitement that we still feel echoes of today. Within a few months, M. K. Wu, C. W. (Paul) Chu, and collaborators, had discovered superconductivity in YBa₂Cu₃O_6+x with a T_c > 77 K, the boiling temperature of liquid nitrogen. At the 1987 March Meeting of the American Physical Society, there was a post-deadline session on high T_c materials that started at 7 pm and lasted through early morning. It made the front page of the New York Times as the “Woodstock of Physics” [2].