• high Tc superconductivity;
  • off-diagonal long-range order;
  • cuprates;
  • pnictides;
  • Coulomb repulsion

A key question in the theory of high-temperature superconductivity is whether off-diagonal long-range order can be induced wholly or in large part by repulsive electronic correlations. Electron pairs on cuprate and the iron-based pnictide and chalcogenide alternant lattices may interact with a strong short-range Coulomb repulsion and much weaker longer range attractive tail. Here, we show that such interacting electrons can cooperate to produce a superconducting state in which time-reversed electron pairs effectively avoid the repulsive part but reside predominantly in the attractive region of the potential. The alternant lattice structure is a key feature of such a stabilization mechanism leading to the occurrence of high-temperature superconductivity with inline image or sign alternating s-wave or s± condensate symmetries. © 2013 Wiley Periodicals, Inc.