  We report the Raman scattering measurements on the triple layer
Bi2Sr2Ca2Cu3O10 (Bi2223) crystals of four different doping levels from slightly
overdoped to strongly underdoped regimes. We observed a double pair-breaking
peak in the antinodal B1g configuration that we attribute to the two antinodal
gaps opening on the outer and inner CuO2-plane (OP and IP) band, respectively.
The doping dependence of the pair-breaking peak energy was investigated.
Considering the difference in doping level between the IP and OP, all the B1g
pair-breaking peak energies for OP and IP were found to align on a single line
as a function of doping, which is consistent with the previous results on the
double and mono-layer cuprates. Within our experimental accuracy the IP and OP
peaks start to appear almost at the same temperature. These findings suggest
some sort of interaction between the layers. The observed gap energy is very
large, not scaling with Tc.
