Mechanically and electrically tunable Rashba-Edelstein effect in ferroelectric semiconductors, CsGeX3 (X=I, Br,<…

The ability of materials to convert charge current into spin current is fundamental to many spintronics applications. One means of realizing this conversion is via Rashba-Edelstein effect (REE). Using density functional theory simulations, we predict that REE can be induced in the recently discovered family of semiconducting ferroelectrics, CsGeX₃ (X=I, Br, Cl). The effect is quantified through Rashba-Edelstein coefficients, χxy=-χyx, which are nonzero in valence and conduction bands. The largest values, obtained for CsGeI₃, are 3.45×10¹⁰ A0.16em0excm and 0.97×10¹⁰ A0.16em0excm in the conduction and valence bands, respectively. The values are comparable to, and sometimes exceed, those of other inorganic materials, although the maximal values occur away from the band edges. The coefficients' sign couples to the direction of spontaneous polarization, offering opportunities for nonvolatile spin current manipulation via external electric field. Furthermore, these coefficients are highly tunable through strain engineering owing to strain-induced variations in spin textures and energy isosurfaces. Specifically, χ in the valence band of CsGeI₃ is enhanced to 3.61×10¹⁰ A0.16em0excm under 5% biaxial strain. Given this potential, we synthesized CsGeI₃ to validate our simulation structure and found excellent agreement between experiment and simulation, thereby allowing extrapolation of our findings to practically significant temperatures. Our study identifies promising materials for nonvolatile, multifunctional spintronic applications.