Mechanical crease in 2D materials—A platform for large spin splitting and persistent spin helix

Abstract

Spin-based information processing promises energy-efficient next-generation electronics, crucial amid the growing energy demands of artificial intelligence. Materials with large spin-split electronic states with exotic persistent spin helix (PSH) texture are critical for such devices; however, only a few materials in nature meet the strict symmetry requirements for PSH texture, limiting material options. We report the striking phenomenon that mechanical crease, unique to 2D materials, enables spin splitting and PSH texture by inducing flexoelectric polarization and asymmetric hybridization. Using first-principles calculations and analytical models, we demonstrate this effect in various 2D materials and reveal two critical features, curvature-induced band shifts and flexoelectricity-driven spin splitting, which are essential to create PSH texture. Notably, bent 2D MoTe₂ exhibits high spin splitting of ∼0.16 eV and an attractively small spin precession length of ∼1 nm, the best known. This work reveals a fundamental design framework to create elusive PSH states in 2D materials, opening exciting avenues for spin-based electronic devices.