Artificial two-dimensional polar metal at room temperature

Abstract

Polar metals, commonly defined by the coexistence of polar crystal structure and metallicity, are thought to be scarce because the long-range electrostatic fields favoring the polar structure are expected to be fully screened by the conduction electrons of a metal. Moreover, reducing from three to two dimensions, it remains an open question whether a polar metal can exist. Here we report on the realization of a room temperature two-dimensional polar metal of the B-site type in tri-color (tri-layer) superlattices BaTiO${}_3$/SrTiO${}_3$/LaTiO${}_3$. A combination of atomic resolution scanning transmission electron microscopy with electron energy loss spectroscopy, optical second harmonic generation, electrical transport, and first-principles calculations have revealed the microscopic mechanisms of periodic electric polarization, charge distribution, and orbital symmetry. Our results provide a route to creating all-oxide artificial non-centrosymmetric quasi-two-dimensional metals with exotic quantum states including coexisting ferroelectric, ferromagnetic, and superconducting phases.

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• Coexistence of polar displacements and conduction in doped ferroelectrics: an ab initio comparative study
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• Recent Advances in Unconventional Ferroelectrics and Multiferroics
• Multiband Quantum Criticality of Polar Metals
• Multiferroic metal-PbNb${}_{0.12}$Ti${}_{0.88}$O${}_{3-\delta }$ films on Nb-doped STO
• Charge order from structured coupling in VSe${}_2$
• Unconventional crystal field splitting in non-centrosymmetric BaTiO${}_3$ thin films
• Effect of strain and doping on the polar metal phase in LiOsO${}_3$
• Spin-Phonon Resonances in Nearly Polar Metals with Spin-Orbit Coupling
• Influences of spin-orbit coupling on Fermi surfaces and Dirac cones in ferroelectric-like polar metals
• Visualizing quantum phenomena at complex oxide interfaces: an atomic view from scanning transmission electron microscopy
• Metallic interfaces in a CaTiO${}_3$/LaTiO${}_3$ heterostructure
• Beyond being free: glassy dynamics of SrTiO${}_3$-based two-dimensional electron gas
• Phonon-Induced Collective Modes in Spin-Orbit Coupled Polar Metals
• Metallic ferroelectric-ferromagnetic multiferroics in strained EuTiO${}_{3-x}$H${}_x$
• Observation of a Room Temperature Two-dimensional Ferroelectric Metal
• Magnetoresistance in Metallic Ferroelectrics