Observation of the superconducting-insulating transition in a   BiSr(La)CuO thin film tuned by varying the oxygen content
  We have conducted a highly precise doping controlled experiment on a thin film of the single layer cuprate Bi2Sr2-xLaxCuOy (x = 0.6), in order to observe the superconducting insulating transition (SIT). Sr2+/La3+ substitution (x = 0.6) allowed us to start from a doping state in the vicinity of the SIT, which was further finely-tuned by varying the oxygen content in very small amounts through a vacuum anneal process. Measurements of the Hall effect at 300K and of the resistance vs. T, R(T), have been performed after each treatment. Approaching the SIT from the metallic side, and with decreasing T, R(T) exhibits a high T metallic behaviour down to a temperature Tmin, followed by a non metallic increase (dR/dT< 0) up to a maximum at Tp before the superconducting transition at Tc. This re-entrant behaviour in R(T), commonly observed in cuprates close to the SIT, is attributed to a phase segregation phenomenon in the presence of strong electronic correlations and inhomogeneities. We present our results extracted from R(T) and Hall effect studies in the region close to the SIT and in the insulating region. A phase diagram shows the characteristic temperatures versus doping. 
I Matei, Z Z Li and H Raffy