The Landé factors of electrons and holes in lead halide perovskites: universal dependence on the band gap

Abstract

The Landé or g-factors of charge carriers are decisive for the spin-dependent phenomena in solids and provide also information about the underlying electronic band structure. We present a comprehensive set of experimental data for values and anisotropies of the electron and hole Landé factors in hybrid organic-inorganic (MAPbI3, MAPb(Br0.5Cl0.5)3, MAPb(Br0.05Cl0.95)3, FAPbBr3, FA0.9Cs0.1PbI2.8Br0.2, MA=methylammonium and FA=formamidinium) and all-inorganic (CsPbBr3) lead halide perovskites, determined by pump-probe Kerr rotation and spin-flip Raman scattering in magnetic fields up to 10 T at cryogenic temperatures. Further, we use first-principles density functional theory (DFT) calculations in combination with tight-binding and k ⋅ p approaches to calculate microscopically the Landé factors. The results demonstrate their universal dependence on the band gap energy across the different perovskite material classes, which can be summarized in a universal semi-phenomenological expression, in good agreement with experiment.

Landé g factors in tetragonal halide perovskite: A multiband k.p model

“…The main k.p parameters were deduced, in this work, from optical absorption experiments, but the result does not completely agree with recent experimental results [25,26]. Calculations with a quasicubic symmetry and tight-binding approaches have also been proposed [28]. In this empirical tight-binding calculation, a large difference from the experiments is obtained.…”

“…Note that in Ref. [28], the authors also measured the components of the Landé tensor in the MAPbI 3 crystal but we do not make a comparison with these experimental results because the authors highlighted that the main axes are tilted with respect to the cubic axes and underlined the possibility of a monoclinic phase or a rotation of the crystallographic axes with respect to the laboratory frame. Using the hole Landé factor of Ref.…”

“…Experimental studies on the Landé factors of electrons and holes are very few. Table III summarizes the experimental results obtained for MAPbI 3 and CsPbBr 3 in bulk materials [18,26,28], polycrystalline materials [17,52], and nanocrystals [27,52,53]. There is no experimental proof of anisotropy of the electron or hole Landé factors in the plane perpendicular to the c axis.…”

“…When these applications include the use of an applied magnetic field, knowledge of the Landé factors for both the electron and the hole is of prime importance. Experimental studies on bulk * kais.boujdaria@fsb.rnu.tn or polycrystalline films materials are very sparse [24] and concern mainly CH 3 NH 3 PbI 3 (MAPbI 3 ) [17,19,[25][26][27] and CsPbBr 3 [18,28]. An anisotropic Landé factor is obtained in particular for the last two materials.…”

“…In the k.p approach, for CsPbBr 3 , the authors of Ref. [28] wrote the electron and hole Landé factors as a function of four k.p parameters in a quasicubic symmetry. They deduced these k.p parameters by fitting their experimental results and found a negative value for the tetragonal crystal field, in disagreement with recent density functional theory (DFT) calculations [30,31].…”