Infrared Absorption and [CuO_5] Pyramid of High T_c Superconductor Bi-Sb-Sr-Ca-Cu-O System

摘要

The infrared absorption spectra of different superconducting phase of high T_c super-conductor Bi-Sb-Sr-Ca-Cu-O system have been measured. The results show that only in the range of 400 cm~(-1)-700 cm~(-1), there is a group of peaks which changes with different super-conducting phases. According to group theory and infrared spectra of CuO, this group of peaks could be assigned to be the [CuO_6] octahedron, the [CuO_5] pyramid and the [CuO_4] plane quadrilateral, but not Cu-O plane or Cu-O chain. Furthermore, the quasi-three dimensional Cu-O layers consisting of [CuO_5] pyramids and proper coupling between them are essential factor for high T_c. It seems that the weaker compling of layers, the higher T_c.