Dynamical study of the spin Hall effect from interchain polaron hopping in organics

Using an extended Su-Schrieffer-Heeger model including spin-orbit coupling and a nonadiabatic dynamics method, the dynamic picture of spin Hall effect (SHE) from interchain hopping of polarons is revealed in a finite organic polymer ladder. The results demonstrate that the transverse hopping of the polaron between chains under an electric field causes a spin-resolved longitudinal motion of the polaron along the chain. The direction of longitudinal transport remains opposite for the initial spin-up and spin-down polarons, which induces a pure spin current carried by polarons. By means of the statistical average over two kinds of polarons with different initial spins, an obvious oscillating SHE is achieved. Spectrum analysis from Fourier transform of spin signal shows a low-frequency part and a high-frequency part in the spectrum. The low-frequency part is attributed to the intrinsic electron dynamic oscillation in the finite-size system in the presence of polarons and the adopted periodic boundary, and the high-frequency part is due to the spin-flip spin dynamics. In addition, we found that the charge-spin conversion efficiency from the interchain polaron hopping may be larger than that from the intrachain polaron transport by one order, which confirms the enhancement of charge-spin conversion efficiency by organic anisotropy. This work deepens our understanding on the mechanism of organic SHE from polarons hopping, as well as the merit of organic anisotropy in the realization of a large SHE.