Strong Disorder and High Temperature Superconductivity
  ARPES and wide area, high resolution STM studies of a micaceous cuprate high temperature superconductor have shown strong nanoscale gap disorder, but the question of whether this disorder is intrinsic and necessary for HTSC, or merely incidental to either this material, or even only its surface, appears to be an open one. We present the case that it is merely incidental, and then review the evidence that strong disorder is actually an essential factor in generating this unprecedented phenomenon. 
J. C. Phillips