The case for dx − y pairing in the cuprate superconductors

The nature of the orbital structure of the pairs in the superconducting phase of the high-temperature superconducting cuprates remains one of the central questions in this field. Here we examine the possibility that the superconducting state of these materials is characterized by d_{x² ? y²} pairing. We begin by looking theoretically at why this type of pairing might be favored in a strongly correlated system with a short-range Coulomb interaction. Then we turn to the experimental question of how one would know if d_{x² ? y²} pairing were present.