Effects of Disorder on Coexistence and Competition between   Superconducting and Insulating States
  We study effects of nonmagnetic impurities on the competition between the superconducting and electron-hole pairing. We show that disorder can result in coexistence of these two types of ordering in a uniform state, even when in clean materials they are mutually exclusive. 
M. V. Mostovoy, F. M. Marchetti, B. D. Simons, and P. B. Littlewood