title: Strain-Induced Ferroelectric Topological Insulator.
abstract: Ferroelectricity and band topology are two extensively studied yet distinct properties of insulators. Nonetheless, their coexistence has never been observed in a single material. Using first-principles calculations, we demonstrate that a noncentrosymmetric perovskite structure of CsPbI3 allows for the simultaneous presence of ferroelectric and topological orders with appropriate strain engineering. Metallic topological surface states create an intrinsic short-circuit condition, helping stabilize bulk polarization. Exploring diverse structural phases of CsPbI3 under pressure, we identify that the key structural feature for achieving a ferroelectric topological insulator is to suppress PbI6 cage rotation in the perovskite structure, which could be obtained via strain engineering. Ferroelectric control over the density of topological surface states provides a new paradigm for device engineering, such as perfect-focusing Veselago lens and spin-selective electron collimator. Our results suggest that CsPbI3 is a simple model system for ferroelectric topological insulators, enabling future studies exploring the interplay between conventional symmetry-breaking and topological orders and their novel applications in electronics and spintronics.
authors.affiliation: Geophysical Laboratory, Carnegie Institution for Science , Washington, DC 20015, United States.
authors.forename: Shi
authors.initials: S
authors.lastname: Liu
authors.affiliation: The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.
authors.forename: Youngkuk
authors.initials: Y
authors.lastname: Kim
authors.affiliation: The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.
authors.forename: Liang Z
authors.initials: LZ
authors.lastname: Tan
authors.affiliation: The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Rappe
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D002586:Cesium / Q000737:chemistry*; D004560:Electricity; D004581:Electronics / Q000295:instrumentation; D004583:Electrons; D004867:Equipment Design; D007454:Iodides / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D008958:Models, Molecular; D049329:Nanostructures / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D044367:Phase Transition; D011312:Pressure; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D017610:Calcium Compounds; D007454:Iodides; D010087:Oxides; C059910:perovskite; D002586:Cesium; D007854:Lead; D014025:Titanium
keywords: Halide perovskites; electron focusing; spintronics; strain engineering; topological surface states