Unusual Mott transition in multiferroic PbCrO3

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 50; pp. 15320 - 15325
• Main Authors: Wang, Shanmin, Zhu, Jinlong, Zhang, Yi, Yu, Xiaohui, Zhang, Jianzhong, Wang, Wendan, Bai, Ligang, Qian, Jiang, Yin, Liang, Sullivan, Neil S, Jin, Changqing, He, Duanwei, Xu, Jian, Zhao, Yusheng
• Format: Journal Article
• Language: English
• Published: United States National Acad Sciences 15.12.2015; National Academy of Sciences
• Subjects: Physical Sciences; Mott transition; multiferroics; Mott criticality; PbCrO3; isostructural transition
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1510415112

The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. Turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by "bandwidth" control or "band filling." However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. Here, we report 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. For the first time to our knowledge, these findings validate the scenario conceived by Mott. 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. The anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking.