Tunneling STM/STS and break-junction spectroscopy of the Pb-doped Bi2223 superconductor (original) (raw)

The combined scanning tunneling microscopy/spectroscopy (STM/STS) and the break-junction tunneling spectroscopy (BJTS) measurements of the three-layered Pb x Bi 2x Sr 2 Ca 2 Cu 3 O 10+y cuprate superconductors were carried out. The averaged dI/dV spectrum obtained by the STS shows the gap ∆ STS ≈ 45 meV, while that of BJTS shows ∆ BJ ≈ 35 meV. In case of the BJTS measurements, we also referred the zero bias (ZB) peak as being due to the maximum Josephson current I Jc. The product of I Jc and normal resistance R N (I Jc R N) was obtained I Jc R N ≈ 3.5 mV at T = 11 K, which is one order lower than that of the BCS-based Ambegaokar-Baratoff theory with ∆ BJ =35 meV taken into account. With increasing the temperature, the I Jc R N was reduced and vanished just below the T c (≈ 106 K), indicating the bulk superconductivity. Simultaneously, from the temperature dependence of the gap features from 80 K to 120 K, the gap ∆ was shown to persist across the T c , indicating that the I Jc R N product is a significant parameter for understanding the cuprate superconductivity.