• Sanjay Shah

      Articles written in Bulletin of Materials Science

    • Two-component model for optical conductivity in Y-Ba-CuO superconductors

      Dinesh Varshney Sanjay Shah R K Singh

      More Details Abstract Fulltext PDF

      The optical conductivity of optimized doped YBa2Cu3O7-δ (δ=0·0,Tc=92 K) superconductors, which are frequency dependent, has been theoretically investigated based on two-component (Drude and mid infrared terms) approach within the Fermi liquid description. Our approach incorporates the Drude contribution as well as hopping of charge carriers in the model dielectric function along with the structure factor. It explains the anomalies observed in the optical measurements for the normal state as the frequency dependence of optical conductivity using the Drude term which gives a sharp peak at zero frequency, and a long tail at higher frequencies, i.e. in the infrared region. The extra term (hopping carriers) gives a peak value in the optical conductivity centred in the mid infrared region. The two species of charge carriers contribution to the conduction in the CuO chain layer as well as CuO2 layer will account for the optical conductivity in the mid infrared as well as infrared frequency regions. The analysis reveals an interesting relation$$\sigma _{CuO_2 layer} \approx 3\sigma _{chain layer} $$, and the nature for optical conduction with energy is similar qualitatively, the only difference is quantitatively. It is shown that the analysis is consistent with the published data on optical conductivity in optimized-doped YBa2Cu3O7-δ superconductors.

    • Specific heat studies in Ho-Ba-CuO superconductors: Fermionic and bosonic contributions

      Dinesh Varshney Sanjay Shah R K Singh

      More Details Abstract Fulltext PDF

      The specific heats of superconducting HoBa2Cu3O7-δ (Tc≅ 92 K) have been theoretically investigated in the temperature domain 70 ≤T ≤110 K. The bosonic (phonons) contribution to the specific heat is estimated from Debye model in the harmonic approximation for high temperature expansion (T > θD/2π) using the moments of the phonon density of states. The fermionic constituent as the electronic specific heat is deduced using a suitable trial function above and belowTc. As a next step the contribution of specific heat by charge oscillations (plasmons) are obtained. The theoretical results from bosonic and fermionic terms are then compared with the experimental results. We find that the specific heats from electronic as well as plasmon term are only a fraction of lattice specific heat and in particular, plasmons do not influence the thermal conduction significantly. The implications of the above analysis are discussed.

  • Bulletin of Materials Science | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.