Doping Controlled Superconductor-Insulator Transition in   Bi2Sr2-xLaxCaCu2O8+delta
  We show that the doping-controlled superconductor-insulator transition (SIT) in a high critical temperature cuprate system (Bi2Sr2-xLaxCaCu2O8+delta) exhibits a fundamentally different behavior than is expected from conventional SIT. At the critical doping, the sheet resistance seems to diverge in the zero temperature limit. Above the critical doping, the transport is universally scaled by a two-component conductance model. Below, it continuously evolves from weakly to strongly insulating behavior. The two-component conductance model suggests that a collective electronic phase separation mechanism may be responsible for this unconventional SIT behavior. 
Seongshik Oh, Trevis A. Crane, D. J. Van Harlingen, and J. N. Eckstein