Dynamics of spin helices in the one-dimensional <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>X</mml:mi><mml:mi>X</mml:mi></mml:mrow></mml:math> model

Motivated by cold-atom experiments and a desire to understand far-from-equilibrium quantum transport, we analytically study the dynamics of spin helices in one-dimensional $\mathit{XX}$ model. We use Jordan-Wigner transformation map chain onto noninteracting Fermi gas with simple equations motion. The resulting are nontrivial, however, as spin-helix initial condition corresponds highly nonequilibrium distribution fermions. find separation timescales between in-plane out-of-plane dynamics. gain insights from analyzing case uniform semiclassical One our key findings is that correlation functions decay ${t}^{\ensuremath{-}1/2}$ at long time, contrast experimentally observed exponential decay.