Pressure-induced metal-insulator transition in oxygen-deficient LiNbO${}_3$-type ferroelectrics

Abstract

Hydrostatic pressure and oxygen vacancies usually have deleterious effects on ferroelectric materials because both tend to reduce their polarization. In this work we use first-principles calculations to study an important class of ferroelectric materials - LiNbO${}_3$-type ferroelectrics (LiNbO${}_3$ as the prototype), and find that in oxygen-deficient LiNbO${}_{3-\delta }$, hydrostatic pressure induces an unexpected metal-insulator transition between 8 and 9 GPa. Our calculations also find that strong polar displacements persist in both metallic and insulating oxygen-deficient LiNbO${}_{3-\delta }$ and the size of polar displacements is comparable to pristine LiNbO${}_3$ under the same pressure. These properties are distinct from widely used perovskite ferroelectric oxide BaTiO${}_3$, whose polarization is quickly suppressed by hydrostatic pressure and/or oxygen vacancies. The anomalous pressure-driven metal-insulator transition in oxygen-deficient LiNbO${}_{3-\delta }$ arises from the change of an oxygen vacancy defect state. Hydrostatic pressure increases the polar displacements of oxygen-deficient LiNbO${}_{3-\delta }$, which reduces the band width of the defect state and eventually turns it into an in-gap state. In the insulating phase, the in-gap state is further pushed away from the conduction band edge under hydrostatic pressure, which increases the fundamental gap. Our work shows that for LiNbO${}_3$-type strong ferroelectrics, oxygen vacancies and hydrostatic pressure combined can lead to new phenomena and potential functions, in contrast to the harmful effects occurring to perovskite ferroelectric oxides such as BaTiO${}_3$.

References in corpus (23)

• A beginner's guide to the modern theory of polarization
• A ferroelectric-like structural transition in a metal
• Strain controlled oxygen vacancy formation and ordering in CaMnO${}_3$
• Comparative first-principles studies of prototypical ferroelectric materials by LDA, GGA, and SCAN meta-GGA
• Magnetic Moment Collapse-Driven Mott Transition in MnO
• `Ferroelectric' Metals Reexamined: Fundamental Mechanisms and Design Considerations for New Materials
• Comparison of the Electronic Structures and Energetics of Ferroelectric LiNbO3 and LiTaO3
• Ferroelectric Instability under Screened Coulomb Interactions
• Band alignment at metal/ferroelectric interfaces: insights and artifacts from first principles
• Pressure-Driven Metal-Insulator Transition in Hematite from Dynamical Mean-Field Theory
• BaNiF4: an electric field-switchable weak antiferromagnet
• Electronic structure of rare-earth impurities in GaAs and GaN
• Cooperative Couplings between Octahedral Rotations and Ferroelectricity in Perovskites
• Crystal-field splitting for low symmetry systems in ab initio calculations
• Doping and temperature-dependent optical properties of oxygen-reduced BaTiO3-d
• Theoretical and experimental evidence of a site-selective Mott transition in Fe2O3 under pressure
• Oxygen vacancies induced ferroelectricity in relaxors with ABO3 structure
• Interplay between Ferroelectricity and Metallicity in BaTiO${}_3$
• Emergence of quantum critical charge and spin-state fluctuations near the pressure-induced Mott transition in MnO, FeO, CoO, and NiO
• Pressure-driven metal-insulator transition in BiFeO${}_3$ from Dynamical Mean-Field Theory
• Pressure-induced enhancement of non-polar to polar transition temperature in metallic LiOsO${}_3$
• Coexistence of polar displacements and conduction in doped ferroelectrics: an ab initio comparative study
• A large modulation of electron-phonon coupling and an emergent superconducting dome in doped strong ferroelectrics

Cited by in corpus (1)

• Dynamical structural instability and its implication on the physical properties of infinite-layer nickelates