  We discuss the characteristic features of triple Cu-O2 layer cuprates
superconductors, by comparing those of single and double layer cuprates
superconductors. After a brief introduction to multilayer cuprates and their
characteristic properties such as the doping imbalance between the inner and
outer Cu-O2 planes (IP and OP, respectively) revealed by nuclear magnetic
resonance, we present the experimental results of angle resolved photoemission
and Raman scattering spectroscopy for the triple layer Bi2Sr2Ca2Cu3O10+z which
showed two different superconducting gaps opening on the IP and OP. The doping
dependence of the double peak structure in Raman spectra was found to be
qualitatively consistent with that of single and double layer cuprates, if each
layer doping for the IP and OP is taken into account. The fact that the IP and
OP share the same electronic phase diagram and the same transition temperature
(Tc) hints to a coupling between the IP and OP. Moreover, the energies of IP
and OP Raman peaks were found to be very large, not scaling with Tc, which can
be attributed to the strong influence of the pseudogap of the underdoped IP in
triple layer cuprates. These findings suggest that the high Tc and the large
gap ratio of triple layer cuprates are realized through a combination of the
interlayer coupling between the OP and IP and the interaction between
superconductivity and the pseudogap.
