Tunable Magnetism and Insulator–Metal Transition in Bilayer Perovskites

Abstract

Two-dimensional (2D) transition-metal oxide perovskites greatly expand the field of available 2D multifunctional material systems. Here, based on density functional theory calculations, we predicted the presence of ferromagnetism orders accompanying with an insulator-metal phase transition in bilayer KNbO3 and KTaO3 by applying strain engineering and/or external electric field. Our results will contribute to the applications of few-layer transition metal oxide perovskites in the emerging spintronics and straintronics. Freestanding transition-metal oxide perovskites have been successfully synthesized, which opened a promising door to design applications in low-dimensional multifunctional electronic devices [1-6]. Compared to conventional 2D materials, such as graphene or transition-metal dichalcogenides [7-9], freestanding perovskite systems are believed to present enriched functionalities from the strongly correlated states in accompany with fascinating oxygen octahedron distortions [10-16]. Recently, oxide perovskites membranes have been demonstrated to exhibit giant tetragonality, flexibility, polarization [1], piezoelectricity [3] and super-elasticity [2]. Most of the interest was mainly focused on properties related to mechanics under the quantum confinement, leaving their electronic and magnetic properties with definitely similar fundamental scientific importance largely unexplored.Bulk KNbO3 (KNO) and KTaO3 (KTO) perovskites have been studied for over 70 years [17]. The former is famous as room-temperature lead-free ferroelectric material [18], while the latter is so-called incipient ferroelectric [19]. Some exotic properties based on them have been realized by doping, size, dimension or interface engineering, including the magnetic response in nanocrystalline KNO, two-dimensional electron gas

Highly Confined Phonon Polaritons in Monolayers of Perovskite Oxides

“…Computational details are provided in the Supporting Information using refs and − . We use tetragonal symmetry for the unit cells of the perovskite-oxide monolayers, which have been found and predicted for various compounds. ,, We show the in-plane lattice constants of our fully relaxed tetragonal structures (space group P 4 mm , no. 140) and of hBN (space group P 6 3 / mmc , no.…”

“…At the same time, the class of 2D materials has consistently been growing, involving more and more systems beyond van der Waals materials. − Particularly intriguing materials are perovskite oxides, which are known to display rich phenomena in their bulk phases, including high-temperature superconductivity, metal–insulator transitions, and multiferroicity . Recently, freestanding membranes of perovskite oxides have been created, − whose thicknesses reach down to the monolayer limit, and which are highly tunable with homogeneous and inhomogeneous strain. − ,,− Because perovskite oxides conventionally possess large effective ionic charges, they are promising candidates for light-matter interactions in the 2D limit.…”