Curvature induced out-of-plane spin accumulation in Rashba quantum waveguides

In this work, we show that (real space) curvature in the geometry of curved waveguides with Rashba spin orbit interactions (RSOIs) can lead to out-of-plane spin accumulations. We first derive the RSOI Hamiltonian on arbitrarily curved surfaces. We then analyze the effects of curvature with two distinct methods. We first apply an adiabatic approximation on gently curved, planar waveguides lying flat on the xy plane to show that analogous to the acceleration of the charge carriers by an electric field, the change in the momentum direction of the charge carriers as they move along the waveguide leads to an out-of-plane spin accumulation. We then use the Heisenberg equations of motion to establish the relationships between spin currents and accumulations on non-planar waveguides. These relations predict the existence of out-of-plane spin accumulation on asymmetrically curved, non-planar waveguides. We finally solve for the eigenstates on such waveguides numerically and present numerical results to verify our analytic predictions. Published by AIP Publishing.