Mott Transition in PbCrO3

Figure caption: Pressure–temperature phase diagram for Mott transition between α- and β-PbCrO3.
Figure caption: Pressure–temperature phase diagram for Mott transition between α- and β-PbCrO3.

The original concept of “Mott transition” was proposed as the screening of Coulomb potential at high pressures, which has been experimentally validated recently. New HPCAT experiments provide direct experimental evidence of a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of ∼3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrent with the collapse, it transforms from a hybrid multiferroic insulator to a metal. Close to the Mott criticality at ∼300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid–gas transition. Both the large lattice volume and the large Coulomb potential in the low-pressure insulating phase are associated with the ferroelectric distortion, which is substantially suppressed at high pressures. Findings of the associated Mott critical behaviors, magnetic and ferroelectric properties, and the isostructural phase transition are fundamentally and technologically important for the study of correlated systems. (S. Wang, et al., Proc. Natl. Acad. Sci. US,  doi: 10.1073/pnas.1510415112