Multigap superconductivity in doped p-type cuprates

Andreev and tunneling spectroscopy studies of Bi2Sr2Ca n − 1Cu n O2n + 4 + δ, HgBa2Ca n − 1Cu n O2n + 2 + δ and Tl2Ba2Ca n − 1Cu2n + 4 + δ have shown that superconductivity in single-layer (n = 1) and two-layer (n = 2) phases has a single-gap character. Qualitatively different results were obtained for three-layer phases. In doped p-type Hg-1223, Bi-2223, and Tl-2223 samples two (or three) superconducting gaps were observed. The existence of multigap superconductivity in superconducting cuprates with n ≥ 3 is explained by a difference in doping levels of outer (OP) and internal (IP) CuO2 planes.