Nonequilibrium phase winding and its breakdown at a chiral interface

We describe a nonequilibrium phase winding of the liquid-crystal director at a flat cholesteric-isotropic interface. The physical origin of the driving force is a symmetry-allowed coupling between an equilibrium helix structure and gradients in impurity concentration set up at an interface forced to move by displacing the sample in a temperature gradient. We interpret these observations to evaluate the coupling constant: ‖${\nu }_{\mathit{c}}$‖=3×${10}^{\mathrm{-}4}$ dyn/cm. A second transition is observed at higher displacement speeds to an orientationally disordered state.