Abstract
de Gennes first pointed out, in the 1970s, the geometric analogy between the layers of a smectic liquid crystal and the phase structure of the wave function of a superconductor. He showed that a layered structure expels twist deformations just as a superconductor expels a magnetic field, with twist penetrating only at the edges of a layer. We calculate how twist penetrates the edge of a small circular disc of a single isolated smectic A layer composed of chiral fd virus particles subjected to a depletion interaction. We find that under certain conditions small discs with a twisted edge are at least metastable, relative to large discs and other possible structures. We see samples in which such small discs appear to be stable for long periods of time.