Fig. 4.

Crystal structure and the phase diagram. (A) Three-dimensional structure of Bi2212 (26), indicating the main crystallographic directions. Relevant to our work are the red arrows, which show the atomic movements in the in-plane breathing mode (Left) and those in the out-of-plane buckling mode (Right). (B) The doping dependence of the coupling constant (λ) along the [010] and [110] directions in Bi2212 (blue and red dots, respectively) and its anisotropy (Δλ between the two directions; black solid line), and λ along the [010] and [110] directions in Bi2223 (green and orange dots, respectively) and the extrapolated anisotropy (black dashed line). A qualitative sketch of the upper critical field and Cooper-pair coherence length (green and violet lines) is also shown (21).