Critical angle for the Brochard-Leger wall in liquid crystals

The existence of a critical angle for the Brochard-Leger (BL) wall in liquid crystals has been investigated experimentally. The experiment shows that there doubtless exists a critical angle ${\mathrm{\phi }}_{\mathit{c}}$ for the BL wall. When the tilted angle of the external field is larger than ${\mathrm{\phi }}_{\mathit{c}}$, the BL wall becomes unstable and will quickly disappear in the sample. The experiment supports an earlier theoretical analysis [X. Y. Wang, Phys. Rev. A 32, 3126 (1985); Phys. Lett. 112A, 402 (1985)].