C. U. Jung — Page 3

arXiv2000

Synthesis and characterization of the infinite-layer superconductor Sr_{0.9}La_{0.1}CuO_{2}

We report the high-pressure synthesis of the electron-doped infinite-layer superconductor Sr_{0.9}La_{0.1}CuO_{2}. A Rietveld analysis using X-ray powder diffraction data showed that, within the resolution of the measurement, the sample was purely an infinite-layer structure without any discernible impurities. The superconducting volume fraction and the transition width were greatly improved compared to those in the previous reports. Also the irreversibility field line was much higher than that of (La,Sr)_{2}CuO_{4}. The higher value seems to originate from the strong interlayer coupling due to the reduced average distance between the CuO_{2} planes.

cond-mat.supr-con↗

arXiv2000

Two-Dimensional Nature of Four-Layer Superconductors by Inequivalent Hole Distribution

The magnetization of the four-layer superconductor CuBa_{2}Ca_{3}Cu_4O_{12-δ} with T_c\simeq117 K is presented. The high-field magnetization around T_c(H) follows the exact two-dimensional scaling function given by Tešanović and Andreev. This feature is contrary to the inference that the interlayer coupling becomes strong if the number of CuO_2 planes in a unit cell increases. Also, the fluctuation-induced susceptibility in the low-field region was analyzed by using the modified Lawrence-Doniach model. The effective number of independently fluctuating CuO_2 layers per unit cell, g_{\rm eff}, turned out to be \simeq 2 rather than 4, which indicated that two among the four CuO_2 layers were in states far from their optimal doping levels. This result could explain why CuBa_{2}Ca_{3}Cu_4O_{12-δ} shows two-dimensional behavior.

cond-mat.supr-con↗