First-principles calculation of the transition temperature Tc for HgBa2CuO4+δ high-temperature superconductors via dipolon theory

Abstract

First numerical evaluations of Tc for oxygenated and argon-reduced single-layered HgBa2CuO4+δ superconductors have been presented. Our calculations are based on the dipolon theory and are found to provide an explanation for the occurrence of superconductivity in single-layered high-Tc superconductors. Relevant expressions useful for the evaluation of Tc have been given. Since the polarizabilities of the ions are not known exactly for the present systems we have performed calculations making use of Pauling's as well as Tessman, Kahn, and Shockley's polarizabilities in order to estimate the uncertainties in the calculated values of Tc associated with uncertainties in the polarizabilities. The effective charges on the ions required for the evaluation of dipoles and dipolon frequencies have been obtained by means of the bond-valence sums. Without fitting with any parameters, our calculations yield Tc values equal to 80±21 K for the oxygenated and 50±27 K for the argon-reduced HgBa2CuO4+δ superconductors, in agreement with the corresponding experimental values 95 and 59 K. The uncertainties in the calculated values of Tc arise because of the uncertainties in various physical parameters (including polarizabilities) used and due to errors involved in the calculations. The present results are consistent with the observed electronic Raman-scattering intensities which show anomalously broad peaks extended up to several electron volts in cuprate high-Tc superconductors. Our calculated dipolon density of states predict four optical absorption peaks at about 77 cm−1, 195 cm−1, 1.6 eV, and 2.5 eV.

Source-reported materials — not catalogue approval

Similar papers