High-temperature superconductors: Playgrounds for broken symmetries

Abstract

Studies of symmetries and the consequences of breaking them have led to deeper understanding in many areas of science. The high-temperature superconductors, discovered in 1986, motivated an unprecedented worldwide flurry of research, not only because applications are promising, but because they also represent a new state of matter that breaks certain fundamental symmetries. In this narrative for nonspecialists, we provide a general background on broken symmetries and superconductivity. Then we show how planar tunneling spectroscopy can detect the broken symmetries of gauge (superconductivity), reflection (d-wave superconducting order parameter), and time-reversal (ferromagnetism). © 2005 American Institute of Physics.