Anomalous superconducting properties at magic doping levels in under-doped La2-xSrxCuO4 single crystals

Abstract A series of high-quality under-doped La 2− x Sr x CuO 4 superconductor crystals with x =0.063–0.125 were prepared by traveling-solvent floating-zone (TSFZ) technique. We found by dc magnetic measurements that, in this series of crystals, the superconducting transition was quite sharp around x =1/16 and 1/9 while it was much broader at other hole densities, and the Meissner fraction showed a remarkable minimum in the close vicinity of x =1/9. We concluded that these anomalies near the `magic numbers' are reflections of intrinsic properties of this cuprate system. Our observations are discussed in light of recently proposed composite charge model together with charge inhomogeneity and electronic phase separations.