Disorder driven metal-insulator transition in BaPb(1-x)Bi(x)O₃ and inference of disorder-free critical temperature.

We performed point-contact spectroscopy tunneling measurements on single crystal BaPb(1-x)Bi(x)O(3) for 0≤x≤0.28 at temperatures T=2-40  K and find a suppression in the density of states at low bias voltages that is characteristic of disordered metals. Both the correlation gap and the zero-temperature conductivity are zero at a critical concentration x(c)=0.30. Not only does this suggests that a disorder driven metal-insulator transition occurs before the onset of the charge disproportionated charge density wave insulator, but we also explore whether a scaling theory is applicable. In addition, we estimate the disorder-free critical temperature and compare these results to Ba(1-x)K(x)BiO(3).