Electron-phonon interaction in barium-potassium-bismuth-oxygen superconductor by quantum path integral molecular dynamics (QPIMD).

Abstract

We have introduced two different techniques in this paper to investigate the high Tc superconductor BaK BiO₃. The first one is the rigid-ion molecular dynamics model to calculate classical properties of the crystal. This method provides the ionic anisotropic vibrational spectra. It is found that the oxygen modes dominate the vibrational spectrum from 150 cm⁻¹ up to 820 cm⁻¹. An increase in the number of substituted K around an oxygen favors high frequency vibrational modes. We have also determined by experiment IR spectrum. The absorption peaks are between 380 to 880 cm⁻¹. Our experimental and computational data are in good agreement in the high frequency region. The second technique used to investigate this high Tc superconductor is based on a quantum path integral molecular dynamics. It has been applied for the first time to the determination of electron-phonon interaction energy. We estimate the electron phonon coupling constant at about 1.34. This value represents a weak to moderate electron-phonon coupling in Ba₁₋ₓKₓBiO₃ in agreement with current views of this pairing mechanism in this material.