Rashba SOC — Spin Texture on Fermi Surface

H = ℏ²k²/2m + αR(k×ẑ)·σ. Rashba spin-orbit coupling splits the Fermi surface into two helical sheets with winding number ±1. Spins lock perpendicular to k — origin of the Berry phase π and topological Hall effect.

α_R (SOC) 0.80 μ (Fermi E) 1.00 k-density 24

Berry phase inner/outer: π / π (topological winding ±1)