Two effects of iodine intercalation on T c in Bi 2Sr 2Ca 1−xY xCu 2O 8: Two-dimensionality and charge transfer

Abstract

Effects of the stage-1 iodine-intercalation on T c have been investigated in Bi 2Sr 2Ca 1− x Y x Cu 2O 8. The iodine intercalation produces two large effects; one is enhancement of the two-dimensionality due to expansion of the crystal along the c-axis, and the other is increase of conductive 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 T c by about 10 K and that the latter effect shifts the x dependence of T c to larger x values by about 0.05 because of the increase of conductive hole carriers by about 0.025 per CuO 2 unit. It has been concluded that the decrease in T c through the I intercalation in Bi 2Sr 2CaCu 2O 8 is due to both effects.