The Role of Mass of Doped Atoms in the Superconductivity of Cu0.5Tl0.5Ba2Ca2Cu3O10−d and Cu0.5Tl0.5Ba2Ca2Cu1.5 M1.5O10−d (M = Cd, Zn, and Ni)

Abstract

For the investigation of any possible role of the mass of atoms in the mechanisms of higher T c superconductivity, we have synthesized Cu0.5Tl0.5Ba2Ca2Cu3O10−d and Cu0.5Tl0.5Ba2Ca2Cu1.5 M 1.5O10−d (M = Cd, Zn, and Ni) samples by two-step solid-state reaction method at 860°C. The synthesized samples have shown orthorhombic crystal structure, and the unit cell volume increases with the doping of M atoms. A suppression in the onset temperature of superconductivity and zero-resistivity critical temperature is observed with the doping of Cd; whereas, these parameters are enhanced with the doping of Ni and Zn. In FTIR absorption measurements, the apical oxygen mode of type Tl–OA–Cu(2) mode is hardened with the incorporation of M = Cd, Zn, and Ni atoms, confirming the doping of these elements in the final compound. In excess conductivity analyses, a suppression is observed in the values of coherence length ξ c (0), inter-layer coupling J and the Fermi velocity V F of carriers with the doping of Cd; whereas the values of these parameters are enhanced with Zn and Ni doping. However, Cd atoms have also been found to induce the enhancements of flux-pinning characters as B c0 (T), B c1 (T), and J c (0); whereas the values of these parameters are suppressed in Ni- and Zn-doped samples. A suppression of magnetic field penetration depth (λ p.d) and the Ginzburg-Landau (GL) parameter κ are observed in Cd-doped samples. The energy required to break apart the Cooper pairs is suppressed in the Cd-doped samples showing that Cd-doped samples promotes weak superconductivity These studies confirm that doped Cd atoms induce anharmonic oscillations in the solid-state medium which suppress the density of phonons and hence the density of Cooper pairs that stress the importance of electron-phonon interaction in the mechanism of high T c superconductivity.