Building an AdS/CFT superconductor
  We show that a simple gravitational theory can provide a holographically dual description of a superconductor. There is a critical temperature, below which a charged condensate forms via a second order phase transition and the (DC) conductivity becomes infinite. The frequency dependent conductivity develops a gap determined by the condensate. We find evidence that the condensate consists of pairs of quasiparticles. 
Sean A. Hartnoll, Christopher P. Herzog, Gary T. Horowitz