Abstract
Recently, it has been demonstrated that CH3NH3PbBr3 exhibits extraordinary giant Rashba splitting, which represents great opportunity for applications in spintronics and orbitronics. In this work, the strain induced Rashba band splitting of CH3NH3PbBr3 with various lattice constants from 5.4 Å to 6.4 Å has been investigated in detail by means of density functional theory including the spin–orbit coupling using full-relativistic pseduopotential. The calculation results indicate that the triple states at the conduction band maximum can be split by both spin–orbit coupling and strain. The details of the band structure at the conduction band maximum further reveal that the Rashba band splitting is strongly anisotropic along different directions due to the distortion of the Pb–Br octahedron. The maximum Rashba coefficient can be up to 2.0 eV Å at the equilibrium lattice constant. Furthermore, the Rashba coefficient is approximately linearly dependent on the strain in the range of ±5%. The Rashba coefficient can be even increased by nearly two times if CH3NH3PbBr3 is compressed by about 5%. Such strain induced Rashba coefficient enhancement may be useful for the application of CH3NH3PbBr3 in spintronic and orbitronic devices.
Highlights
During the past few years, the organic–inorganic lead halide perovskite solar cells have continually achieved improvement in both power conversion efficiency and stability
A closer look at the band structures of CH3NH3PbBr3 at point R shown in Fig. 3(b) reveals that the valence band maximum (VBM) and the conduction band minimum (CBM) are split when the SOC effect is included in the Density Functional Theory (DFT) calculation, resulting in a momentum shift of VBM or CBM away from R
The CBM and VBM are not located at the same point, but with different Rashba momentum offsets, resulting in the indirect bandgap, which is similar to the case of CH3NH3PbI3.40,41 Besides, the energy splittings are different along different directions
Summary
During the past few years, the organic–inorganic lead halide perovskite solar cells have continually achieved improvement in both power conversion efficiency and stability. If a system exhibits SOC and lacks center symmetry, the spin band will split even in nonmagnetic materials.2 Such a phenomenon was first described by Dresslhaus and Rashba.. When the SOC is included, the theoretical bandgap value of CH3NH3PbI3 calculated by DFT is much smaller than the experimental bandgap value.. Kim et al indicated that the helical direction of Rashba band splitting texture can be even controlled by the external electric fields via ferroelectric switching using the first-principles calculation.. Kim et al indicated that the helical direction of Rashba band splitting texture can be even controlled by the external electric fields via ferroelectric switching using the first-principles calculation.17 It was pointed out by Giovanni et al that the circular dichroism existed in the CH3NH3PbI3 thin films during the pump-probe spectroscopy, which suggested novel spintronic device applications of organic–inorganic lead halide perovskite materials.. The calculation results reveal that the Rashba effect can be tuned by the strain
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