Two effects of iodine intercalation on T c in Bi 2Sr 2Ca 1-xY xCu 2O 8. Two-dimensionality and charge transfer
The effects of stage-1 iodine intercalation on Tc have been investigated in Bi 2Sr 2Ca 1- xY xCu 2O 8. The iodine intercalation causes two large effects: one is a change of the two-dimensionality due to an expansion of the crystal along the c-axis, the other is an increase of conducting hole carriers due to charge transfer between intercalated iodine atoms and CuO 2 sheets in the host material. For the stage-1 iodine-intercalation compounds, it has been found that the former effect decreases Tc by about 10 K and that the latter effect shifts the x dependence of Tc to larger x values by about 0.05 because of the increase of conducting hole carriers by about 0.025 per CuO 2 unit. It has been concluded that the decrease in Tc through iodine intercalation in Bi 2Sr 2CaCu 2O 8 is due to both effects.