Effect of carrier distribution on superconducting characteristics of the multilayered high-T-c cuprate (Cu0.6C0.4)Ba2Ca3CuO12+y: Cu-63-NMR study

We report Cu-NMR studies of the multilayered high-T-c cuprate (Cu0.6C0.4)Ba 2Ca3Cu4O12+y (Cu1234) with T-c=117 K. In the normal state, the Knight shift (K) and the nuclear spin-lattice relaxation rate (1/T-1) of Cu-63 give evi dence that the inner CuO2 planes (IP) are underdoped, whereas the outer one s (OP) are heavily overdoped. In the superconducting (SC) state, both K and I/T-1 decrease markedly below T-c=117 K in the IF, whereas in the OP they decrease moderately below T-c=117 K, but markedly below T-c2=60 K. The unus ual NMR results in the OP reveal that the SC gap does not fully develop dow n to T-c2=60 K. From comparison with a conventional d-wave model, it is sho wn that the SC gap in the OP increases linearly below T-c. and follows the mean-field type of T dependence below T-c2 We propose that these dissimilar ities are caused by the large difference of doping levels between the IP an d the OF. The bulk SC transition at T-c = 117 K is considered to be trigger ed by the underdoped IP in Cu1234.