Uncovering large Rashba spin-splitting and persistent spin-helix states in undulated 2D materials

Finding materials with large and unidirectional Rashba spin-orbit coupling (SOC), resulting in persistent-spin helix states with small spin-precession length is critical for advancing spintronics. In this talk, I will present a design principle to create such large and unidirectional Rashba SOC in 2D materials through specific shape undulations. [1] Analytical modeling and first-principles calculations reveal that undulation-induced asymmetric hybridization brings about and even enhances Rashba SOC. Its strength α_R ∝ 𝜅 (bending curvature) and shifting electronic levels Δ ∝ 𝜅². Despite integral curvature vanishes for typical topographies, implying net-zero Rashba effect, our two-band-model and electronic structure calculation of prototype 2D MoTe₂ bent in a generic shape z = f(x) with feasible curvature show that only an interplay of α_R​ and Δ modulations results in large unidirectional Rashba SOC with well-isolated states. Their high spin-splitting ~0.16 eV, and attractively small spin-precession length ~1 nm, belong among the best known. Our work enhances understanding of the physical effects of undulations on Rashba SOC in 2D materials and opens new avenues of using their topographical deformation for spintronics and quantum computing.

[1] arXiv:2410.16242