Enhanced Superconducting Gaps in the Trilayer High-Temperature Bi2Sr2Ca2Cu3O10+δ Cuprate Superconductor

We report the first observation of the multilayer band splitting in the optimally doped trilayer cuprate Bi2Sr2Ca2Cu3O10+delta (Bi2223) by angle-resolved photoemission spectroscopy. The observed energy bands and Fermi surfaces are originated from the outer and inner CuO2 planes (OP and IP). The OP band is overdoped with a large d-wave gap around the node of Delta(0) similar to 43 meV while the IP is underdoped with an even large gap of Delta(0) similar to 60 meV. These energy gaps are much larger than those for the same doping level of the double-layer cuprates, which leads to the large T-c in Bi2223. We propose possible origins of the large superconducting gaps for the OP and IP: (1) minimal influence of out-of-plane disorder and a proximity effect and (2) interlayer tunneling of Cooper pairs between the OP and IP.