Pair correlation and dynamic Jahn-Teller effect: high Tc in nanoclusters
  Electronic states in metallic nanoclusters form energy shells and degree of their filling depends on the number of delocalized electrons. In the region close to half-filling the cluster geometry oscillates between the prolate and oblate configurations (dynamic Jahn-Teller effect). For large clusters this effect competes with pair correlation and, as a result, it is perfectly realistic to observe the transition to the superconducting state. For some clusters the value of the critical temperature is rather high, near 140K 
Vladimir Kresin, Yurii Ovchinnikov, Jacques Friedel
cond-mat.supr-con cond-mat.mes-hall