Fig. 2
Calculated charge susceptibility for Bi2223. a, b Calculated charge susceptibility along the Cu-O direction [q = (h, 0)] and the diagonal direction [q = (h, h)] in the normal a and superconducting (SC) b states in Bi2223. The calculations are performed for a tight-binding band structure with a d-wave SC order parameter Δk = Δ[cos(kxa) − cos(kya)]/2. Tight-binding hopping parameters are taken from ref. 23 and Δ is set to 60 meV. The dotted lines indicate the constant q cut plotted in c. c Constant q plot of Imχc(q, ω) at q = (0.15, 0) in the SC and normal states, and their difference spectrum
