• Amit K Khaskalam

      Articles written in Bulletin of Materials Science

    • Oxygen deficiency dependence of transition temperature in (Sm, Er) Ba2Cu3O7−δ superconductors

      R K Singh Dinesh Varshney Amit K Khaskalam

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      We have investigated the effects of oxygen deficiency (δ) on the transition temperature (Tc) of (Sm, Er)Ba2Cu3O7−δ superconductors by incorporating the effects of the two dimensional (2D) acoustic phonons and plasmons in the framework of strong coupling theory. The proposed approach for yttrium cuprates properly takes care of the double CuO2 plane in a unit cell and has been found earlier to be successful in describing the pairing mechanism as well as the variation ofTc withδ in Y Ba2Cu3O7−δ system. The coupling strength (λ), the screening parameter (μ*) and the two dimensional acoustic phonon (plasmon) energyħω+) as a function of oxygen deficiency is worked out. Finally, the transition temperature is evaluated and is found to be consistent with the earlier experimental data on yttrium cuprates. Thus, coupled phonon-plasmon mechanism is adequate to understand the nature of pairing mechanism and oxygen deficiency dependence of transition temperature in 90 K (Sm, Er)Ba2Cu3O7−δ superconductors.

    • Effect of oxygen deficiency (δ) on normal state resistivity of YBa2Cu3O7-δ superconductors

      Dinesh Varshney R K Singh Amit K Khaskalam

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      We have investigated theoretically the effect of oxygen deficiency (δ) on normal state resistivity (ρ) as well as its temperature dependence in YBa2Cu3O7-δ superconductors. This has been based on a potential which incorporates the structure factors and various interactions for double two-dimensional (2-D) conducting CuO2 plane. Using the Coulomb and electron-phonon terms of the interaction potential, we have then worked out the coupling strength (γ) for neighbouring electrons linked via 2-D acoustic phonons (_). Furthermore, the scattering time (τe-ph) due to electron-phonon interaction is deduced. The variations inτe-ph andρe-ph are studied with oxygen deficiency (δ) which is in the range of 0·0≤δ≤1·0, and the results thus obtained are found to be consistent with the earlier reported data. The residual resistivityρ0 obtained by extrapolation from experimental data together withρe-ph will predict the nearly-linear behaviour of normal state resistivity at temperatures (T) [90≤T≤300 K] in YBa2Cu3O7-δ superconductors.

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