Stability of helical textures inHe3-A

In the presence of weak uniform superflow, bulk ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ near $T_c$ assumes a uniform texture with $\hat{l}$ parallel to ${\overrightarrow{\mathrm{v}}}_s$. Below a characteristic temperature $T_h$, however, the temperature dependence of the hydrodynamic free energy can induce a helical deformation. The equilibrium configuration of such helices is investigated, using Cross's weak-coupling gas model with Fermi-liquid corrections to evaluate the hydrodynamic parameters. This model predicts $T_h\approx 0.82T_c$ and that helical textures can be stable at all $T<\mathrm{}{T}_h$ with suitable adjustment of the apex angle and pitch.