Fermi surface nesting in Ba1-xKxBiO3 observed by Compton profile measurement -: art. no. 205106

Compton profiles of Ba1-xKxBiO3 have been measured, where x=0.13 and 0.39, to elucidate the relation between the Fermi surface and the metal-insulator transition. The two-dimensional momentum densities, reconstructed from several directional Compton profiles, are compared with those calculated by band theory. The momentum density of the x=0.39 metallic sample is explained by the predicted Fermi surface, except for one minor difference. Whereas, that of the x=0.13 insulating sample is simply reproduced by the geometry of the fcc-type Brillouin zone, suggesting the disappearance of the Fermi surface at the zone boundaries due to nesting. This result validates the interpretation that the insulating behavior of this system originates from the charge density wave instability.