SINGLE-BAND HUBBARD-MODEL FOR SUPERCONDUCTIVITY AND CHARGE-DENSITY-WAVE ORDER IN THE BISMUTH OXIDE SUPERCONDUCTORS

A model is developed for superconducting and charge-density-wave (CDW) correlations in the bismuth oxide superconductors BaPb1-xBixO3 and Ba 1-xKxBiO3, Starting from the Hubbard model and assuming a three-dimens ional tight-binding band structure. Self-consistent equations for the superconducting gap (DELTA), and the CDW gap (g), and the band filling (N(e)) are derived and solved numerically. Solutions for both DELTA a nd g are obtained for 0.29 less-than-or-equal-to N(e) less-than-or-equ al-to 0.38 and 0.80 less-than-or-equal-to N(e) less-than-or-equal-to 1 .00 (where N(e) = 1.00 represents half-filling). These solutions are c ompared against the experimental data for BaPb1-xBixO3 and Ba1-xKxBiO3 and qualitative agreement is obtained.