D. Varshney et Mp. Tosi, Pairing mechanism and superconducting state parameters of cubic perovskiteBa0.6K0.4BiO3, J PHYS CH S, 61(5), 2000, pp. 683-688
We develop an effective three-dimensional dynamic interaction, which incorp
orates screening of charge carriers by optical phonons and by plasmons, to
discuss the nature of the pairing mechanism leading to superconductivity in
cubic perovskite Ba0.6K0.4BiO3. The potassium-doped barium-bismuth oxide s
ystem (Ba-K-BiO) is treated as an ionic solid containing carriers and a mod
el dielectric function is set up which fulfils the appropriate sum rules on
the ionic and electronic polarizabilities. The values of the coupling stre
ngth and of the Coulomb interaction parameter indicate that the superconduc
tor is in the strong coupling regime. Following strong-coupling theory, the
superconducting transition temperature of optimally doped Ba-K-BiO is esti
mated as 30 K. The energy gap ratio is slightly enhanced and the isotope ex
ponent is severely reduced relative to the Bardeen-Cooper-Schrieffer values
. The present analysis points to the importance of both plasmons and optica
l phonons in determining the effective electron-electron interaction leadin
g to superconductivity in doped cubic perovskites. (C) 2000 Elsevier Scienc
e Ltd. All rights reserved.