Energy gap of Tl-Ba-Ca-Cu-O compounds by tunneling

Abstract Tunneling spectroscopy measurements were carried out on surfaces of polycrystal Tl-Ba-Ca-Cu-O superconductors of two stoichiometric compositions (2212 and 2223). Broad gap-like structures were routinely observed on differential conductance curves, and taking their peak positions and resistive T c 's, we obtain the estimated 2Δ k B T c of ∼ 6 for both compositions which is in good agreement with our earlier tunneling results on oriented film surfaces of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O compounds.