title: Tunable ferroelectric polarization and its interplay with spin-orbit coupling in tin iodide perovskites.
abstract: Ferroelectricity is a potentially crucial issue in halide perovskites, breakthrough materials in photovoltaic research. Using density functional theory simulations and symmetry analysis, we show that the lead-free perovskite iodide (FA)SnI3, containing the planar formamidinium cation FA, (NH2CHNH2)(+), is ferroelectric. In fact, the perpendicular arrangement of FA planes, leading to a 'weak' polarization, is energetically more stable than parallel arrangements of FA planes, being either antiferroelectric or 'strong' ferroelectric. Moreover, we show that the 'weak' and 'strong' ferroelectric states with the polar axis along different crystallographic directions are energetically competing. Therefore, at least at low temperatures, an electric field could stabilize different states with the polarization rotated by π/4, resulting in a highly tunable ferroelectricity appealing for multistate logic. Intriguingly, the relatively strong spin-orbit coupling in noncentrosymmetric (FA)SnI3 gives rise to a co-existence of Rashba and Dresselhaus effects and to a spin texture that can be induced, tuned and switched by an electric field controlling the ferroelectric state.
authors.affiliation: Consiglio Nazionale delle Ricerche-CNR-SPIN, I-67100 L'Aquila, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Stroppa
authors.affiliation: 1] Consiglio Nazionale delle Ricerche-CNR-SPIN, I-67100 L'Aquila, Italy [2] Department of Physical and Chemical Sciences, University of L'Aquila, I-67100 L'Aquila, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Di Sante
authors.affiliation: Consiglio Nazionale delle Ricerche-CNR-SPIN, I-67100 L'Aquila, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Barone
authors.affiliation: Faculty of Physics, Center for Computational Materials Science, University of Vienna, A-1090 Wien, Austria.
authors.forename: Menno
authors.initials: M
authors.lastname: Bokdam
authors.affiliation: Faculty of Physics, Center for Computational Materials Science, University of Vienna, A-1090 Wien, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Kresse
authors.affiliation: Faculty of Physics, Center for Computational Materials Science, University of Vienna, A-1090 Wien, Austria.
authors.forename: Cesare
authors.initials: C
authors.lastname: Franchini
authors.affiliation: Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA.
authors.forename: Myung-Hwan
authors.initials: MH
authors.lastname: Whangbo
authors.affiliation: Consiglio Nazionale delle Ricerche-CNR-SPIN, I-67100 L'Aquila, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Picozzi