Persistent and Quasipersistent Spin Textures in Halide Perovskites Induced by Uniaxial Stress.

Persistent spin textures are highly desirable for applications in spintronics, as they allow for long carrier spin lifetimes. However, they are also rare, as they require a delicate balance between spin-momentum coupling parameters. We used density functional theory simulations to predict the possibility of achieving these desirable spin textures through the application of uniaxial stress. Hybrid organic-inorganic perovskite MPSnBr3 (MP = CH3PH3) is a ferroelectric semiconductor which exhibits persistent spin textures near its conduction band minimum and mostly Rashba type spin textures in the vicinity of its valence band maximum. Application of uniaxial stress leads to the gradual evolution of the valence band spin textures from mostly Rashba type to quasipersistent ones under a tensile load and to pure Rashba or quasipersistent ones under a compressive load. The material exhibits flexibility, a rubber-like response, and both positive and negative piezoelectric constants. A combination of such properties may create opportunities for flexible and rubbery spintronic devices.

First-principles property assessment of hybrid formate perovskites.

Hybrid organic-inorganic formate perovskites, AB(HCOO)3, are a large family of compounds that exhibit a variety of phase transitions and diverse properties, such as (anti)ferroelectricity, ferroelasticity, (anti)ferromagnetism, and multiferroism. While many properties of these materials have already been characterized, we are not aware of any study that focuses on the comprehensive property assessment of a large number of formate perovskites. A comparison of the properties of materials within the family is challenging due to systematic errors attributed to different techniques or the lack of data. For example, complete piezoelectric, dielectric, and elastic tensors are not available. In this work, we utilize first-principles density functional theory based simulations to overcome these challenges and to report structural, mechanical, dielectric, piezoelectric, and ferroelectric properties of 29 formate perovskites. We find that these materials exhibit elastic stiffness in the range 0.5-127.0 GPa; highly anisotropic linear compressibility, including zero and even negative values; dielectric constants in the range 0.1-102.1; highly anisotropic piezoelectric response with the longitudinal values in the range 1.18-21.12 pC/N; and spontaneous polarizations in the range 0.2-7.8 µC/cm2. Furthermore, we propose and computationally characterize a few formate perovskites that have not been reported yet.