Multigap superconductivity in doped p-type cuprates

Andreev and tunneling spectroscopy studies of Bi 2 Sr 2 Ca n − 1 Cu n O 2 n + 4 + δ , HgBa 2 Ca n − 1 Cu n O 2 n + 2 + δ and Tl 2 Ba 2 Ca n − 1 Cu 2 n + 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) CuO 2 planes.