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1. Structural descriptor for enhanced spin-splitting in 2D hybrid perovskites

   https://doi.org/10.1038/s41467-021-25149-7  

   Jana, Manoj K.; Song, Ruyi; Xie, Yi; Zhao, Rundong; Sercel, Peter C.; Blum, Volker; Mitzi, David B. (December 2021, Nature Communications)

   null (Ed.)

   Abstract Two-dimensional (2D) hybrid metal halide perovskites have emerged as outstanding optoelectronic materials and are potential hosts of Rashba/Dresselhaus spin-splitting for spin-selective transport and spin-orbitronics. However, a quantitative microscopic understanding of what controls the spin-splitting magnitude is generally lacking. Through crystallographic and first-principles studies on a broad array of chiral and achiral 2D perovskites, we demonstrate that a specific bond angle disparity connected with asymmetric tilting distortions of the metal halide octahedra breaks local inversion symmetry and strongly correlates with computed spin-splitting. This distortion metric can serve as a crystallographic descriptor for rapid discovery of potential candidate materials with strong spin-splitting. Our work establishes that, rather than the global space group, local inorganic layer distortions induced via appropriate organic cations provide a key design objective to achieve strong spin-splitting in perovskites. New chiral perovskites reported here couple a sizeable spin-splitting with chiral degrees of freedom and offer a unique paradigm of potential interest for spintronics. 

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2. Large exchange-driven intrinsic circular dichroism of a chiral 2D hybrid perovskite

   https://doi.org/10.1038/s41467-024-46851-2  

   Li, Shunran; Xu, Xian; Kocoj, Conrad A.; Zhou, Chenyu; Li, Yanyan; Chen, Du; Bennett, Joseph A.; Liu, Sunhao; Quan, Lina; Sarker, Suchismita; et al (March 2024, Nature Communications)

   Wei, Mengjie (Ed.)

   In two-dimensional chiral metal-halide perovskites, chiral organic spacers endow structural and optical chirality to the metal-halide sublattice, enabling exquisite control of light, charge, and electron spin. The chiroptical properties of metal-halide perovskites have been measured by transmissive circular dichroism spectroscopy, which necessitates thin-film samples. Here, by developing a reflection-based approach, we characterize the intrinsic, circular polarization-dependent complex refractive index for a prototypical two-dimensional chiral lead-bromide perovskite and report large circular dichroism for single crystals. Comparison with ab initio theory reveals the large circular dichroism arises from the inorganic sublattice rather than the chiral ligand and is an excitonic phenomenon driven by electron-hole exchange interactions, which breaks the degeneracy of transitions between Rashba-Dresselhaus-split bands, resulting in a Cotton effect. Our study suggests that previous data for spin-coated films largely underestimate the optical chirality and provides quantitative insights into the intrinsic optical properties of chiral perovskites for chiroptical and spintronic applications. 

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3. Bulk‐Rashba Effect with Suppressed Spin Relaxation in a Polar Phase of Bi _{1‐ x} In _{1+ x} O ₃

   https://doi.org/10.1002/adma.202504684  

   Kang, Deokyoung; Lu, Xue‐Zeng; Acharya, Megha; Husain, Sajid; Harris, Isaac; Behera, Piush; Lin, Ching‐Che; Banyas, Ella; Smith, Alex; Ricci, Francesco; et al (July 2025, Advanced Materials)

   Abstract The Rashba effect enables control over the spin degree of freedom, particularly in polar materials where the polar symmetry couples to Rashba‐type spin splitting. The exploration of this effect, however, has been hindered by the scarcity of polar materials exhibiting the bulk‐Rashba effect and rapid spin‐relaxation effects dictated by the D'yakonov–Perel mechanism. Here, a polar LiNbO₃‐typeR3cphase of Bi_1‐xIn_1+xO₃withx≈0.15–0.24 is stabilized via epitaxial growth, which exhibits a bulk‐Rashba effect with suppressed spin relaxation as a result of its unidirectional spin texture. As compared to the previously observed non‐polarPnmaphase, this polar phase exhibits higher conductivity, reduced bandgap, and enhanced dielectric and piezoelectric responses. Combining first‐principles calculations and multimodal magnetotransport measurements, which reveal weak (anti)localization, anisotropic magnetoresistance, planar‐Hall effect, and nonreciprocal charge transport, a bulk‐Rashba effect without rapid spin relaxation is demonstrated. These findings offer insights into spin‐orbit coupling physics within polar oxides and suggest potential spintronic applications. 

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4. Tunable optical properties and stability of lead free all inorganic perovskites (Cs ₂ SnI _x Cl _6−x )

   https://doi.org/10.1039/c7ta10040j  

   Zhu, Weiguang; Xin, Guoqing; Wang, Yiping; Min, Xin; Yao, Tiankai; Xu, Wenqian; Fang, Minghao; Shi, Sufei; Shi, Jian; Lian, Jie (January 2018, Journal of Materials Chemistry A)

   Organic–inorganic hybrid lead-based perovskites experience significant environmental instability under ambient moist air and are not environmentally benign due to the usage of toxic Pb. Here, we report a new approach to synthesize lead-free all inorganic perovskites (Cs 2 SnI x Cl 6−x ) using hydriodic acid (HI) demonstrating greatly enhanced environmental stability and tunable optical properties by controlling the I − /Cl − ratios. Single phase perovskites can be achieved with a low iodine or chlorine content, and a phase separation occurs in the binary system with closer iodine and chlorine dopings. UV-vis diffuse reflectance and photoluminescence measurements reveal tunable band gaps of Cs 2 SnI x Cl 6−x perovskites from the UV to the infrared region. The mixed halide perovskite with a lower chloride content shows significantly higher photoluminescence intensity. The thermal stability of mixed halide all-inorganic perovskites is continuously improved as the Cl content increases. The synthesis of Sn-based perovskites with tunable optical properties and environmental stability represents one step further toward the realization of the stable lead-free all inorganic perovskites. 

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5. Tuning Rashba type spin–orbit field via Mn composition gradient engineering in (Ga,Mn)As ferromagnetic films

   https://doi.org/10.1063/5.0278247  

   Lee, Taehee; Jana, Apu K; Lee, Sanghoon; Liu, Xinyu; Furdyna, Jacek K (August 2025, APL Materials)

   The study investigated how out-of-plane structural inversion asymmetry (SIA) influences current induced spin–orbit fields (SOFs) in crystalline (Ga,Mn)As ferromagnetic films. By growing (Ga,Mn)As films in which the manganese composition is gradually increased or decreased along the growth direction of the film, we systematically control the out-of-plane SIA in the films. Using Hall measurements designed to probe current-induced SOFs, we identify both Dresselhaus-type SOF, arising from bulk inversion asymmetry, and the Rashba-type SOF, originating from SIA of the films. While the sign of the Dresselhaus-type SOFs remains unchanged regardless of the out-of-plane asymmetry direction (i.e., ascending or descending order variation of Mn composition in the film), the Rashba-type SOFs exhibit opposite orientations depending on the Mn gradient along the growth direction. These results provide direct experimental evidence of out-of-plane SIA-driven Rashba-type SOF modulation and establish a robust platform for engineering spin–orbit torque phenomena in ferromagnetic semiconductor systems. 

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