Unusual Mott transition in multiferroic PbCrO ₃

Abstract

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.

Band gap crossover and insulator–metal transition in the compressed layered CrPS4

“…6) follows a scaling behavior of ðσ À σ c Þ $ ðP À P c Þ 1 γ with a critical exponent of γ = 3 and the critical pressure P c of 13(1) GPa. Similar scaling behavior has been observed in the conductivity of Crdoped V 2 O 3 48 and PbCrO 3 49 . The temperature-dependent data below 10 GPa measured from room temperature to 420 K (inset of Fig.…”

Regulating Exciton–Phonon Coupling to Achieve a Near‐Unity Photoluminescence Quantum Yield in One‐Dimensional Hybrid Metal Halides

“…By fitting the unit‐cell volume to the Birch–Murnaghan equation of state, [ 15 ] a volume collapse can be observed, which is a common feature for the isostructural transition. [ 16 ] The structural changes observed in the XRD results are also reflected in the pressure‐dependent absorption spectra (Figure S2 , Supporting Information), suggesting the significant effects of pressure on the atomic and electronic structures. In addition, the obtained electronic structures by density‐functional theory calculations well reproduce the variation trend of experimental bandgaps (Figure S11 , Supporting Information).…”

Breakdown of Hooke’s law of elasticity at the Mott critical endpoint in an organic conductor

“…Whenever the Mott transition can be tuned by pressure, which is the case for many systems, such as various κ-(BEDT-TTF) 2 X ( 21 , 22 , 42 ) or Et x Me 4– x Z [Pd(dmit) 2 ] 2 ( 43 ) organic charge-transfer salts, as well as transition metal oxides, such as (V 1– x M x ) 2 O 3 ( 24 , 44 – 46 ), NiO ( 47 ), or PbCrO 3 ( 48 ), the Mott endpoint will eventually be governed by critical elasticity. A different situation is encountered in VO 2 , where doping experiments suggest that the transition is insensitive to pressure so that the elastic coupling is expected to be weak.…”