Fermi surface nesting in Ba1−xKxBiO3

Three-dimensional momentum densities were reconstructed from experimental Compton profiles of Ba1−xKxBiO3, where x = 0.10 (insulating) and x = 0.37 (metallic) by Hiraoka et al. The momentum densities exhibit significant differences between the metallic and insulating samples. The momentum densities in the insulating sample are interpreted to represent the filled, polyhedral Brillouin zone for fcc-type crystals, displaying a feature of the perfectly nested Fermi surface, suggesting the disappearance of the hole-pockets that are predicted by the theory to be around the X points in the Brillouin zone. The momentum densities in the x=0.37 metallic sample resemble those predicted by band theory based on the local-density approximation, but still show an unusual feature due to Fermi-surface nesting. A weak nesting feature of the Fermi surface was observed near the L points.

The momentum densities on the (001) planes in extended zones (before folding) for x=0.37 in d) and x=0.10 in h). In each panel the LDA calculations are at left and experimental results at right.

Hiraoka N., Buslaps T., Honkimäki V., Ahmad J., Uwe H. - Fermi surface nesting in Ba1-xKxBiO3 observed by Compton scattering: Three-dimensional momentum density reconstruction study - Phys. rev., B 75, 121101-1-121101-4 (2007).
Hiraoka N., Buslaps T., Honkimäki V., Minami H., Uwe H. - Fermi surface nesting in Ba1–xKxBiO3 observed by Compton profile measurement - Phys. rev., B 71, 205106-1-205106-6 (2005).